http://www.torontoairsoft.com/CYMA-A...ck_p_2316.html
The cap doesnt sell by itself. Under folders are pretty fragile, so having a spare stock isn't too bad of ideal. There is a reason why the Russians switched over to side folding stocks. Ritz said locktite or glue on the new cap that is a good ideal. Also tighten the tiny hex screw that holds the cap in place.