Need Piston rings

What kinda engine?
If it's a generic 66/80cc engine, then go here:
2 bicycle Motorized BIKE GAS ENGINE -80cc piston rings | eBay

No picture, but I have bought them, and they are a fit.

I agree with rohmell I bought similar rings at
eBay - Piston Rings

and these fit fine for me on my 69/80cc engine.

need to revive this thread, are there any special methods for installing new piston rings? or is it just put the new ones in and go?

I have no problem installing by myself. You might want a spare pair of hands. You might want to start with the piston removed. Ease apart (too much, you'll snap another ring) the ring while slipping it over the piston..One from the bottom the other from the top. Pay attention to the piston pins in the groves. Turn cylinder upside down, compress rings with fingers and push/bump the piston down, only so that the top ring is in the cylinder. Next go for the second (bottom ring), and push/tap the piston down and the ring in the cylinder. The extra hands will push the piston while you compress the rings. Slide cylinder with the piston over the studs, insert the wrist pin and then the clip. Tap cylinder all the way down and into place. These pistons and rings go in easy...DON'T force the piston into the cylinder, or you have a chance to break another ring. You might want to lube before hand.
Ring compressors are nice but not necessary. We don't have a spring behind a oil scraper rings like in a auto. Those need a ring compressor. This way you can use the bottom of the opening in the skirt to compress the rings with your fingers..Make sure the ring groves are clean and pins inserted. Take a broken ring, and scrape any carbon out. I usually have to brake a ring to do this.