Can't remember the links off hand, USA Belting and American Belting I think. There is another one that I bought my spare belt from, but I can't remember the name - cheap and free shipping. Shoup's prices are pretty average on belts.
I've got one baler with alligators and one with clippers, much prefer the alligator style.
Call them and talk to them about your baler, some of the most knowledgeable folks I've talked to on Vermeer balers. Plus I didn't feel like I was bothering them at all with my questions, something all too uncommon these days.