Try Oregon Barrel Company, which is affiliated with The Gun Works in Springfield, Oregon. I'll admit I have no first-hand experience with them, but I have read several articles or forum posts about rifles built around their barrels, and I have yet to see anything negative. I believe their maximum length for rifle barrels is 35" and I don't think they make swamped barrels, but they offer straight octagon, tapered octagon, OTR, and round barrels in all of the standard calibers with virtually any groove type or twist rate. I think Mike Nesbitt had C. Sharps build a black powder cartridge rifle around an Oregon Barrel rifled to his specs, and he was pretty happy with it. I called them once about doing a re-bore and was advised that they don't do that. They only make new barrels. However, they will make drop-in replacement barrels for T/C rifles on a custom order basis.
I have one pistol and one rifle with Hoyt barrels. Robert Hoyt is best known on this forum for his work re-boring and lining barrels, but he also makes them from scratch. He does good work. However, the word is that he is not taking any orders until April, and at that point will only be doing T/C type re-bores for a while until he catches up.
Charlie Burton makes barrels that are highly regarded. I don't know for sure that he makes fast twist barrels, but he probably does. For what it's worth, I've been waiting five years and three months for a custom barrel from him, with no firm delivery date set so far.
Rice Barrel Co. has recently updated their website and it looks as if they have expanded their offerings. I don't know that they have what you need, but it won't hurt to look, or maybe give them a call.
I would definitely check out Oregon Barrels, though.
Notchy Bob