LaMonte, If you are in a bind and need to fix this really quick, most Ace hardware stores carry "Flair-it" plumbing fittings. Any 1/2" valve has the same retainer cap you are looking for. I bought a bag of caps from the manufacturer for 93 cents each because if one cracked and let go, you probably have others about to fail. Merry Christmas & Blessings, Fred