I’m not sure about full weight, but here’s where I’d check:
1. In Chengdu, try Decathlon, located right across the street from Ikea. They have frisbees for sure (I bought some to take to Zebra music festival) but I’m not sure if they’re full weight or not. Decathlon is a French sports supply store though and they generally carry much higher quality items than you’d find at a similar Chinese chain.