Where can I get ono of those heavy duty rear hubs?

I am really impressed by the sealed bearing, made to be motorized rear hubs. I have seen them described in the GruBee website but he only sells wholesale and I only need one. They seem like the right part for the task at hand. The rear wheel hub does seem like the weak link in the chain as regular bicycle wheels were never designed to handle 2+ horsepower. It seems like it could get ugly real fast if the rear axle came apart under power. GruBee sells lots of other neat stuff, is there anyone out there handeling this stuff retail?