Ebikes with Bafang motors are your way to go: The FLX Roadster uses a Bafang Max Drive, Luna Cycles sell a Bafang BBSHD and 52v battery mounted to a KHS SixFifty 200 MTB, or if you want a cruiser the Biktrix Stunner is $200 more and uses a Bafang BBS02 that you ask them to program to Class 3.