Giant in the Playground's Increasing Size, Effective Size, Unarmed Damage, Reach thread is of some limited utility.

Minmaxboard's Grappling Handbook, Hulkamania is runnin' wild, is of somewhat more use.

From your current position, I suggest the following.

Option 1: Sorcerer

No, really. Enlarge Person as a spell gives you +5 to your grapple modifier. It comes in a cheap wand at your level. Babau Slime increases your grapple damage with a bunch of acid (scales with caster level, buy a higher CL wand). Fearsome Grapple is a level 2 spell, so 4500gp, i.e. 'you can afford it', and adds +4 to your grapple mod. Another level 2 is Balor Nimbus, 6d6 to anyone grappling you per round. Corrosive Grasp creates multiple touch attacks, so you do normal grapple damage and it sets off the touch attack for +1d8 acid each time. Fist of Stone gives +6 enh to strength and a natural slam attack, but only for a minute. Of course, timing all this short-duration buffing requires an ambush on your part, so why not buy a wand of Chameleon to help hide, or Invisibility for sneaking around.

You'll also have an Octopus familiar from Stormwrack, for another +3 to grappling.

Sorcerer avoids having to make use magic device checks to use the wands - if you have a friendly arcane caster willing to sneak along with you and buff you for your grappling ambush, then you can forgo this option entirely.

Option 2: Warblade

Non Tome of Battle classes count as half initiator level for determining eligibility for maneuvers. So a level in Warblade with your 11 other levels counts as a 6th level Warblade, meaning you can select 3rd level maneuvers. A 3rd level maneuver (it's a stance) is Crushing Weight of the Mountain. It gives you the Constrict ability. Other than a Soulmeld, this is one of very few ways to get Constrict in the game without changing shape. Constrict is amazing, because ANY TIME YOU ROLL A GRAPPLE CHECK, even to /enter/ a grapple, to do unarmed damage, when they try to escape, WHATEVER, you get to do Constrict damage. Yes, in addition to your unarmed strike, yes, in addition to entering the grapple damage, yes every time they try to escape. You just squeeze the life right out of them. Crusader provides a better chassis, and also has Crushing Weight of the Mountain, but warblade has access to Iron Heart Surge which is very barbarian.

Option 3: Totemist

At level 2 in Totemist from Magic of Incarnum, you grow an extra pair of arms and add your essentia x 2 + 4 to your grapple mod. At this level, with the Expanded Soulmeld Capacity (Totem) feat, that's +12 to grapple. Also grants extra natural attacks from the arm, and other stuff from other soulmelds (short-range teleport, Spell Resistance, Natural Armour, Fire Resistance, etc).

Doesn't really do much for you this level, though. A good choice to take after you've dipped the low-hanging fruits in Warblade and/or Sorcerer.

Feat: Scorpion's Grasp

From Sandstorm, this feat lets you basically have improved grab for unarmed strikes and one-handed weapon attacks. It lets you punch someone, grab them, succeed on a grapple attempt, punch them again, and still have the rest of your actions free to punch people. The best part of Improved Grab, however, which is grappling at a -20 to count as not grappled and building a big ball of weak enemies that you carry around with you and use as a melee weapon, is sadly absent.

Feat: Snatch

Requires claws or bite, MMII. Gives Improved Grab, and the ability to fling creatures 3 sizes smaller than you far, far away. Totally awesome.

Feat: Open Lesser Chakra (Arms)

Combined with a level in Totemist to get access to Kraken Mantle, binding the Mantle to your newly opened Arms slot will give you +2 to grapple per Essentia placed in (max 3, for +6 to grapple untyped).

Item: Gloves of Titan's Grip

From MiC, 3/day activate to get +8 Enhancement to Grapple for 7 rounds. Strength boosts are usually enhancement, but nothing really enhancements grapple except Grip of Iron, so this is great. Totally great. Buy it.

Item: Scorpion Claws

From Sandstorm. Exotic weapon that grants +4 to grapple checks. Well worth it, possibly even if you're not proficient.

Notes

Scaled Horror prestige class from Savage Species requires the 'Aquatic' or 'Reptilian' subtypes. You could make an argument that as a Dragon Disciple, you're kind of doing that. If so, it picks up Improved Grab at first level. Warblade -> Scaled Horror would be a great power boost.

Black Blood Cultist from Champions of Ruin is normally great for grapplers, but you're too high level and it overlaps with Dragon Disciple, also your alignment is wrong. Avoid it entirely.

Psychic Warrior is a great class for grapplers, but at this level you get too little benefit and too few power points to be of any use. The two key powers are Grip of Iron and Expansion, but they both want Augmentation to be great. There are more Wizard/Sorc spells that benefit grappling than there are powers, so even if you grabbed some Dorjes, it wouldn't be as worth it as a Sorc dip. Check the second link for more spells/powers that help out grappling.

Aberration Blood - This feat sets you up for Inhuman Reach, a natural reach increaser. It also adds +2 to grapples. At this level, it's probably sub-par.

I'm guessing someone else will soon cover the more "beaten path", so I'm looking at all sorts of exotic sources for feats, prestige classes or spells. Also since you didn't mention anything about the backstory, settings or character of this orc barbarian (typical) / bard (less common) / dragon disciple (wait, what?!), I'm guessing you put more weight on improving grapple than on a coherent theme (please correct me if I'm wrong). So, here goes:

Unusual Grappling Boosters

1. Lords of Madness Aberrant Feats

The aberration guide introduces "Aberration feats", essentially, your ancestor was an aberration or the result of an aberration's experiment to improve its humanoid thralls. There are several such feats, all stemming from Aberration Blood. I'm quoting only the relevant details:

Aberration Blood [Aberrant]
Prerequisite: Humanoid.
Benefit: You gain a physical feature that grants you a racial bonus on one type of check;
[...]
You cannot change it later. The bonus must be chosen from the following list:
[...]
Flexible Limbs [benefit: +2 on grapple checks]

After that, you gain access to Inhuman Reach and Deepspawn:

Inhuman Reach [Aberrant]
Your arms elongate, allowing you to touch the floor with your hands. In addition, you can bend them in strange and unnatural ways. The arms may vary in appearance, perhaps seeming scaly and snakelike, or slimy like tentacles; conversly, they may resemble normal but longer arms with a second elbow joint. Unless you wear a large cloak to conceal these deformities, you are disturbing to behold.
Prerequisite: Aberration Blood.
Benefit: You gain additional 5 feet reach. [...] If you already have a reach of more than 5 feet for some reason, this extends your reach by another 5 feet. [...] Your elongated arms also grant you +2 bonus on climb checks.
Special: Due to the disfigured nature of your new limbs, you take a -1 penalty on all melee attack rolls.

and

Deepspawn [Aberrant]
The abnormalities in your aberration-tainted heritage grow more pronounced. Your body undergoes a shocking degeneration into something that is strickingly inhuman.
Prerequisite: Aberration Blood, one other aberrant feat.
Benefit: Two short but powerfull tentacles sprout from your waist. You gain two tentacle natural attacks that each deal 1d4 points of damage (for a Medium creature) plus your Strength modifier. The tentacle attacks are treated as primary weapons.
You can attack with weapons and also make tentacle attacks, but your tentacle attacks are treated as secondary weapons: the attacks are made with a -5 penalty on the attack rolls, and you add only 1/2 your Strength bonus to the damage roll.
You gain +2 racial bonus on grapple checks.

So, following this feat chain will end up in your orc gaining a +4 racial mod to grapple checks, extended reach and two tentacles that deal 1d4+9 damage each (and you can use them in a grapple!) - creepy, but probably effective.

There other (just as disturbing) aberrant feats, but this path seemed most relevant...

2. Libris Mortis Undead Grafts

Not sure if you'd count these as magic items or not. Essentially, find a necromancer / crazy wizard with the Graft Flesh: Undead Grafts feat and pay him to replace some of your body parts with undead grafts (or gain access to a Wish spell and ask for it...) if you have 10 ranks in Heal, you can even learn the feat yourself...
All of the grafts are expensive, disturbing and permanent alteration to your body - but there are benefits... I'm listing some of those relevant to grapple:

Vampiric Fangs (25,000 gp, vampiric touch): This set of sharp teeth replace the creature's existing teeth. The grafted creature gains the ability to drain blood from a living victim with its fangs by making a successful grapple check. If it pins the foe, it drains blood, dealing 1d4 of Constitution damage each round. On each successful drain attack, the grafted creature gains 5 temporary hit points that last for up to 1 hour.
Weakening Arm (40,000 gp, ray of enfeeblement): A weakening arm is a skeletal forelimb that grants a +4 inherent bonus to the grafted creature's Strength. Twice per day, the grafted creature can use a weakening touch. A living creature touched takes 1d6 points of Strength damage. A touch that misses does not count against the daily limit.

Combine the fangs and two arms and you have one disgusting orc, with an inherent +8 to strength, the ability to drain constitution while pinning the opponent (and gain temp HP while doing so), and can do strength damage four times per day (and is also 105,000 gp poorer)

3. Less weird, Just Uncommon Feats and Prestige Classes

From Sandtorm:

Scorpion's Grasp
Prerequisites: Str 13, Improved Unarmed Strike, Improved Grapple.
Benefit: If your attack with an unarmed strike or a light or one-handed weapon hits, the strike deals normal damage and you can start a grapple as a free action; no initial touch attack is required. If you succeed in starting the grapple, you must drop your one-handed weapon, but if you started the grapple with a light weapon, you can use it in each round to make an attack against the creature you are grappling without taking the normal -4 penalty on the attack roll. If you initiated the grapple while armed, however, you cannot make additional grapple checks to deal damage during the round in which you use this feat.

From Frostburn:
The Primeval is a prestige class with stats similar to the Warrior (good BAB advancement, strong Fort save). It has special features which may resonate nicely with what you've already chosen: It goes through regression - permanently losing Int and Cha, but improving Str, Dex, Con and Wis. As a bonus, he can transform into a chosen primeval form (dinosaur, dire 'ice age' mammal etc.) a few times a day.
I'll elaborate more if you are interested.

Requirements
Alignment: Any nonlawful
BAB: +8.
Skills: Handle Animal 5 ranks, Knowledge(Nature) 5 ranks, Survival 5 ranks.
Feats: Endurance, Self-sufficient, Toughness.

The Frostrager is a prestige class which is very similar to the Barbarian, but has some benefits which apply to grappling - for example the first level turns your unarmed attack damage to 1d6 + 1d4 cold damage (+STR modifier, as usual), as well as give you +4 natural armor bonus to AC while raging (plus other benefits). I'll elaborate more if you are interested.

Requirements
BAB: +6.
Skills: Intimidate 4 ranks, Survival 4 ranks.
Feats: Frozen Berserker, Improved Unarmed Strike, Power Attack.
Special: Rage as class ability.
Special: must have been reduced to 0 hp by cold damage (either from magical cold [...] or from exposure to extreme cold environment)

I'll add more when I have more time. please comment if any of these is relevant for you at all...