I've recently been looking into the Gates belt-drive system. (Mostly out of intellectual curiosity since i probably won't be able to afford it.) The first thing I noticed is that it looks strikingly similar to a to a timing belt system on a car, or any number of industrial applications.
After finding the specs (tooth count/pitch for belts and pulleys) on the Gates/carbondrivesystems website,
http://carbondrivesystems.com/cd_specs.php?lang=us, I decided to check my favorite online "hardware" store http://mcmaster.com. It turns out they have belts and pulley in similar sizes (tooth counts and dimensions) to many of the ones produced by Gates. They even have carbon reinforced belts of the same tooth count and pitch (8mm) which is used widely in the automotive world. This got me thinking... how hard would it be to adapt a 50tooth cam gear onto a crank. I would wager that the two below could be adapted to a crank rather easily with minor machine work (milling, drillling/tapping), by the looks of the you could even choose your own offset for correct chain-line (belt-line?)
The rear gear/pulley may not be as easy to source, ( at least one that will fit with minimal modifications) However, it shouldn't be hard to find one with the correct tooth count and pitch since 8mm pitch is pretty standard. I'm thinking a water pump pulley may be the ideal candidate. Here is a Honda timing belt picture, notice 4 different potential rear pulleys, and this is just one car.
Anyways, just wanted to share my recent brainstorming. I intend to go to the junkyard pretty soon and do some poking around and teeth counting. If i can do this for cheap enough I may just try it.