Try this site below, I have never used this product but for 10 bucks I'd try it. One thing to think about though, the reason your tank is sweating is because of cold water in the tank and warm humid air in the bathroom. The warm humid air can be managed somewhat with an exhaust fan. This will also help alleviate mold and mildew problems. Second are you sure your toilet is shutting off? If you have a small leak and the tank is constantly filling with more cold water this will make the sweating worse.