I hadn't thought of boat places or RV supply places. I'll give that a shot and look for the stick on stuff. As long as it stays on it should work fine. I'm just never confident with my grip with those slick stocks.
If you are looking for something that is a little less course you may try a rubber grip material made by Pachmayr called "Pak Skin" it comes pre-cut or in sheets and Midway carries it. I have used it with some success.