Rock River Arms makes a Varmint style rifle, with 16", 18", 20" and 24" barrels. That's if you can find them in stock, they have a 3 to 6 month wait time.
Sometimes you can find one locally though, I got lucky last month and found a 24" model. Shoots great. MIne has the 1 in 8" twist, which is what I wanted.
My friend found another one, but it has the 1 in 12" twist. He's not happy, since he wanted the same twist I got in mine.
Check out Gunbroker, they do turn up from time to time. Stag Arms has a Varmint rifle as well.