I know the last time I was on e-bay there was someone that was parting out a 660 Grizzly and had all the parts listed on there, so like dnhyoung mentioned try looking at that once.
Other wise I know I bought a few things in the past for my Banshee at a place called North County Yamaha and they back then had some real good prices. Web site is www.ncyyamaha.com You can give them a try also if you want.
Ok just saw maybe a good one in the back of Dirt Wheels, it is www.partswarehouse.com the ad say buy direct and save. Just incase the phone number is 1-800-860-0686
Mike