Where are you located??
In Canada, you can get good quality replacement wheels from Royal Distributing by mail (Kimpex, I believe). The bonus is that, unlike Yamaha OE wheels (back axel), they have removable bearings and are about 1/2 the price.....
They have a good online catalogue and good customer service. If you're looking at the coloured wheels, pay the extra 3 or 4 bucks for the more expensive part #.....They are WAAAAY better than the slightly cheaper wheels.
WB.