Another probably-baked idea; please advise if anyone has seen this exact product idea elsewhere.
PROBLEM: An un-insulated toilet tank may "sweat" enough that it drips on the floor and lead to mold and mildew buildup. Insulated tanks and mixer valves are relatively expensive fixes. Drip trays are
ugly and have to be made specifically to fit a variety of tank designs. Fabric toilet tank covers may actually make the problem worse by trapping moisture -- and depending on your own sense of style, it may be hard to find one that isn't ugly.
SOLUTION: A toilet tank "sweatband." A band of highly absorbent fabric a few inches wide and long enough to wrap entirely around the tank. The narrower the band, the less visible it will be. Fabric should be treated with an anti-microbal, anti-mildew agent. The closure should be a combination of elastic with velcro or buttons to allow it to fit a wide range of tank sizes.
PACKAGING: The product should be available in neutral colors as well as designer shades, and packaged in sets of two.
USAGE: Wrap around the toilet tank and position as close to the bottom edge of the tank as possible. As condensation builds up, it may run down the tank sides but will soak into the sweatband (and not drip onto the floor).
When completely soaked, take the band off and hang someplace less humid than your bathroom to dry (or toss it in the clothes dryer). While one band is drying, put the other band on the tank so that it's always protected.