For CVT parts. Treatland.tv has a Lot of parts and upgrades like all the different weights to set the upshift rate etc, and they also have a decent selection of the driven variator springs to fully customize for most mopeds, and with the GY6 being as popular as it is, finding cvt upgrades should be really easy from treatland, ebay, and other scooter parts places online.
If someone needs a monster CVT like for a 40hp engine (or larger), look up "snowmobile clutch" on ebay or google and you'll find all the parts you could use.
I got this little engine from treatland last summer and it has a built in CVT with plenty of upgrades available, they even make new belts for it again so no problem if the belt wears out... https://www.treatland.tv/franco-mori...ete-engine.htm
...Got this one before deciding what to put it in and I'm still undecided, it's about twice as wide as the China Doll engines so I'd need some really wide pedal cranks for a bicycle, but something like the Stingray or one of those 26" chopper type frames might work.
As far as GY6 upgrades tho, there's plenty out there for both the engine and CVT.