I had recently upgraded my 3D printer and am now able to make inserts for the larger 8" wheels. Here's one I made for the 2014 Gen 3 Performer which has the fully covered dome wheel covers, but I think it has the same wheels as the Gen 2 performer with the "gear" inserts.
I took several tries but I think the fit is pretty good now. This one shown is just a raw print which looks a bit rough, actual prints that I make will be cleaned up and fully painted. These will have a lot of room for custom texts compared to the inserts for the 6 inch wheels.
PM me if anyone is interested. Price will be $15 for the standard design with 3 x "WEBER" printed on it plus $3 for shipping. Customs will be $20 plus $3 shipping.