Edit the title to rear hub w/brake. It will be an easy search for others.
No deep linking here http://www.worksman.com/ Act like you're going to order a bike. In the options they list several rear hubs. The one with a brake is for a single speed a lists for $80. Ask if they will sell one seperate or offer you a source. Mention this site.
Best I got...Good luck!
aye augi... I posted there talking about it a day or two ago. Was just curious.
Note: The parts supplier listed in Grubee's site does not carry hubs and things like that due to the massive quantity needed to be ordered apparently. Other parts are the same way so I have no idea that may be the barrier to entry for this is not enough people order the stuff?