Front roller will be driven by whatever I can find, probably a length of climbing accessory cord (nylon stuff as it can be sewn end to end pretty effectively for this purpose) which has a bit of stretch in it to allow adjustment between the different lengths required.
Kreitler belts are about $20, but you could use a band saw blade (for those who love action).
Kreitler belts are about $20, but you could use a band saw blade (for those who love action).