There is something called Parafilm made by American National Can. It's a thermoplastic strip that you stretch around something to seal it. It's good for grafts on plants and sealing dormant paint tubes, but I think it's mainly used by laboratories. One use only. 'Moisture resistant'Real electrical tape is great. I've had a patch on a spray bottle of water for years. Hasn't leaked yet. It contracts in cold and expands in heat, though, so if you apply it at room temperature, go another few inches around if you're going to take it someplace cold. In a pinch, you can probably reseal with the same piece of tape once - if you've kept it clean. I'd probably go with LargeMouthBass's ziplock for the fastest/ easiest solution (throw in some foam so it floats) and the gasket as the nicest.