I am quite sure that hoehn makes the clamp on style tuner. Give him a call at 636-745-8144. The cost is around $200. Its a bit pricey but then the best usually is. You'll need to have a caliper handy to measure your barrel at certain points when you call. This is what I have been told anyway.
I know for a fact that Fudd makes the clamp on type inquire at FUDDHAM@AOL.com.
Dave