Forgot to link the company that made those bikes:
Trailmate for the Lowrider. The engine is sold separately by Honda and needs to be attached by someone with handy skills.
Sunbicycles. Look under recumbents X3 AX Trike. You might be able to find an electric motor designed for this bike. The noise from my 4 cycle Honda is a little too much for some people. It might also not be noticed as a motorized bike.