Not sure if these have the power level you are looking for, but it appears they are in the 90-100hp range:
http://www.raven-rotor.com/
These are based on Suzuki car engines. In a little looking at what they offer, it appears to me that the donor engines are not common in the U.S., but there is ample supply with relatively low-miles from auto recyclers in Japan. There's millions of these Suzukis all over the world, but they were only sold in a couple of models for a couple of years in the U.S. - so best bet is probably to expect to buy a complete engine / PSRU from Raven.
Raven is out of Colorado, if that helps.
There is a Yahoo group for Suzuki engines in general "Flygeo" (there is also a gear-driven PSRU out of a Canadian company for these engines).