well, xpaintball.com should have the proper "blue" hammer o ring, if that is the one you are looking for. there a re a few other sites out there that have them, but, if you got a clear one, give PMI a call their number can be found at
www.buypmi.com, and im more than positive that they will send you a blue one for free, and could possibly help you out with a whole kit (for a price) if you really want one.