I don't know a thing about these transmissions except that they're clever. But I would suggest that one good source for weird belts of all sorts is your local farm store, for farm equipment uses an amazing assortment of belts of all widths and farmers don't appreciate high prices. Our local one is called Tractor Supply Company, and Rural King is another. They also seem to be a good source for fasteners, metric and otherwise (they're selling Mahindra tractors, from India, here in rural Ohio) and there are crazy springs and clutch materials as well.
Mark Kinsler