I know a perfect store(https://www.dkoldies.com/) on US that sells a lot of this stuff and they have huge collection of games for this type of console. I purchase most of my Nintendo games to them. Or do you preferred P2P transaction for this kind of deal.

This is the only store that I know that sells this kind of vintage games except the ebay. They have 120 days warranty for all there items plus points for every purchase. I hope this help.

NES: https://www.dkoldies.com/nintendo-nes/
SNES: https://www.dkoldies.com/super-nintendo/