Once in a while a Hercules W2000 Rotary shows up for sale but they're often in pretty bad shape, whether for lack of parts or knowledge of how to fix it. I spotted this one for sale on eBay and it looks to be in very good condition, according to the owner he had it completely restored.
The Hercules was only built from October 1974 to November 1975. 1784 were built and the leftovers were sold each successive year as that year's model, right up until 1979. The early ones had a gas and oil mix, the later ones used oil injection. The Hercules was one of only a few rotary engine motorcycles to make it to market, the Suzuki RE5 being another as well as the very limited Norton John Player Specials.
Interesting bikes but except for Mazda and a few one offs, rotary engines never seemed to go anywhere.