OEM parts are very hard to find for them. Chinese knock-offs are out there but even they are expensive.
I had one. It was a very fun bike but limited with a top speed of 29mph. No way to make them faster as the Valve Springs are too weak to go any faster safely. This means if you are going down a hill and going faster than 29mph you can have a problem! I am told you can install PC50 Valve Springs for a little more speed.
If you get them... the Carb O-rings are impossible to find. I looked for a number of years. Then decided to contact an O-ring company to have a set made. I now have Kits for the Carbs. The Kit covers both types of carbs. If the Carbs leak or they siliconed yours, to stop them from leaking, PM me for a kit. $30.00 plus shipping.