What ^^^ PC2K said.

If Iodine could be held in plastic, then storing it would be easy. The problem is that iodine is VERY reactive (but this is what makes it work for purifying water). So you need to lovingly wrap the iodine with some material which it will not react with. Glass and teflon fit the bill. I am not a chemist, so I cannot comment on what else might work.