About 15-20years ago, when disks were just beginning to appear on MTB's (originally on high-end downhill bikes) there were bolt-on billet pieces that would let you mount disc rotors and calipers on to a bike that was not originally equipped with discs. I think i saw them in the back of a Mountain Bike Action.
The only disc brake conversion parts i can come up with are some hoplessly cheap ($5) brackets from
China. @
Octopoker - The wheels you linked are heavy chrome steel wheels from an 'industrial' cruiser/klunker like a Worksman, that's been converted with a motor. The site that was selling those wheels is down, so i don't know what they're asking for, but you can get a decent set of alloy MTB wheels for $100-120.