http://www.championtarget.com/shooti...dingstock.aspx
Optics Planet might have the Champion in stock.
http://www.ramlinestocks.com/ramline...#RemingtonMisc
https://www.stockysstocks.com/mcmill...ass-stock.html
http://www.mpistocks.com/
Ive heard a Model 7 stock fits if you use Model 7 lower hardware.
Model 600 & 660:
Any Remington stock can be used for both of these models. However, because each of these models was equipped from the factory with a 18" or 20" barrel, we recommend that you use the Model 7 for the Model 600 since it is the only stock we offer with a short forend. All 600’s must be converted to an ADL trigger guard.