Check out the Home Brew Talk/DIY forum. There is a lot of discussion regarding these in the form of the Miller/Coors home draft systems. Apparently, the home draft things are the same system as the Tap A Draft, but need to be modified in some way to re use them. I think it is much cheaper to buy one of those(invite some people over who don't know any better to drink the Miller Lite) and modify it versus buying a new Tap A Draft system. Just a thought, especially if you like to tinker with things.
Not trying to promote another forum, but I thought this info would be helpful.