As a perfectionist, I am a "prick" to whom I trust for parts as I warranty what I sell or install, many don't.
As I said in # 10 John Dikov is good on some parts. I purchase 72cc jug/piston kits from him, his stock variators are ok, but not great. I may start buying stock heads from him. He is mostly an importer / seller, not a repair guy.
http://valleyscooterparts.com/
John @ tested scooter parts is a both a seller and a repairer and is easy to talk with as well as buy from. Unfortunately his inventory appears to be on an as needed basis. his main site is:
http://www.testedscooterparts.com/
There is a guy out of NC, but he is a pain to deal with, does not respond to emails or calls. But does have decent pricing and good quality. Ships in his own sweet time, so you might have to wait.
The guy I rely on the most as I said is a scooter tuner that posts on CL in Atlanta. He buys the best quality I've seen and in quantities and passes the savings on. He also makes up starter kits of certain things like CVT (gates belt, several GS roller weight sets, clutch springs, and torque / contra springs) at a decent price. Once I had my first kit and tuned it in, now I just order fill in from him as I use it.
As to your other posting, main jet sizes: Those #s are supposed to represent a metric size determination, but I have checked many new and old jets and found it to be NOT uniform. I just make sure the stock jets are clean, then test it (both 5 gas & road). If I find either needs adjusted I wire drill in 0.001" max incrementation, then retest.