A cheap and easy way to seal bottles re-packed with iodine is to use PFTE tape. It is made of teflon, which is one of the few things that iodine will not break down. Those familiar with plumbing or high-pressure air lines have probably used this stuff. It is non-adhesive, but if rapped around the threads of the bottle before you replace the cap it will keep the bottle air-tight. If it works on 150 lb. air lines, it will work at zero lbs. pressure. For extra security, rap entire bottle with the PFTE tape after replacing the lid and then rap again with electrical tape.

Just about any hardware store carries this stuff and it is only a couple bucks for a lifetime supply.

Happy re-packing,
George