If the dwarf is from somewhere with some tech, you could make the dragonbane weapon be a firearm.
My 3.5e DMG is missing, but in the 3.0 DMG, under Futuristic Weapons, Rainaissance Weapons, there are a pistol (1d10) and musket (1d12) which you could use. Presumeably theyre also in the 3.5 dmg. There are also rules for a bomb that does 2d6.
The World of Warcraft RPG book gives rules for a flintlock pistol (2d6), a rifle (3d6) or a Blunderbuss (cone spread 3d6 to all in the spread).
But my Personal favorite for this sort of thing, is the OGL Steampunk book, by Mongoose Press, which has a full page table of different sized firearms ranging from matchlock tech to revolvers. They have one handed, light, and 2 handed firearms, and rules for double barreled, rifled barreled, and steampowered versions of the above, which slightly alter the properties of the weapon. (double barreled gives you one die type smaller, but you're getting 2 of them). It also includes malfunction rules for critical failures with firearms.
For example's sake, I'll list off some of the weapon types and the kind of damage they do.
Light Weapons
Light flintlock Pistol: 1d10, x3 Crit, 60 ft range, malfunctions on a 1-3
One Handed Weapons
Medium Flintlock Pistol: 2d6, x3 Crit, 60 foot range, malfunctions on a 1-3
Heavy Flintlock Pistol: 2d8, x3 Crit, 60 ft. range, malfunctions on a 1-3.
Two Handed Weapons
Blunderbuss: Don't like their blunderbuss.
Musket, Flintlock: 2d8, x3 Crit, 100 foot range, malfunctions on a 1-3.
Furthermore, you could always just invent a Dwarven Cannon of some kind. I'm assuming youre not going to pass these things out like candy, and only the dragon Hunter will have one, just so you know.
Two Handed Weapons
Dwarven Hand Cannon
3d8, x3 Crit, 100 Foot Range, Malfunctions on a 1-3.
Weighs 25lbs.
Takes say, 2-3 Standard Actions to Load.
Ammunition Weighs 3 lbs per shot.
Firing requires 1 lb of smoke powder/gunpowder.
(He starts combat with it pre-loaded).
Use this as well if you like:
Using a firearm (with the exception of the dwarven hand cannon) only requires simple weapons to fire (point and click), but loading and maintenance requires Exotic Proficiency: Firearms. (Make it martial proficiency if firearms are really common).
While I'm pretty sure I can't just give you the malfunction table (I dunno if it's ogc or not) I can give you a different malfunction table that's easier than the big % based one they put in the book.
Roll a d6, then consult the following mini table.
6 - Rattle & Hum: The firearm works normally but makes a loud unpleasant grinding noise.
5 - Fault: The Firearm works but not as intended, and imposes a -4 penalty to hit, with the shot veering off from it's intended target.
4 - Glitch: The Firearm Jams, requiring repairs. The Repairs cost nothing in materials. It will require a DC x check of the appropriate type (up to you) to repair it (I'd make the DCs scale from 10 to 25, or even higher for the cannon.)
3 - Breakdown: The Firearm works, but does 2d4 points of damage to itself, ignoring hardness. Cost to repairs need to be done as in break. If the damage doesn't render the item useless (if it still has more hit points left), it can be used again, but will malfunction again, every time it is used, until the item is repaired.
2 - Broken: The Firearm has broken, and requires a DC x check to fix it, as well as 1/4 the Item's value in appropriately tooled materials. (This one have the DCs range from 25 to 40+, but allow them to repair it over time, such as in town)
1 - Explode: The Firearm Explodes, sending shards and shrapnel everywhere, doing it's damage to the wielder, and half that damage to all creatures in a 10 foot radius of the wielder.
