Uhmm... I'd ask you to site your source. I ask because everyone I know carries a filter as their main item, with chlorine dioxide TABLETS as back up. I only point that out because most of my friends from my childhood joined the military and went the special missions path, and they all give me funny looks because I still use iodine tablets, but crypto isn't an issue around me.

It sounds like what you want is iodine crystals so you can make your own version of a Polar Pure. You can buy them from any chemical supply house, but why bother? You aren't going to be able to buy the small quantity you need from a chem house. So you need to buy and ship a LOT more of a fairly dangerous corosive biocide than you need, then you need to store the leftovers. It's going to be more cost efficient to go with something like Polar Pure.

Have you read the MSDS on iodine? You will need a way to filter the crystals out- in low concentrations, perfectly safe. Injesting macroscopic crystals will give you a new definition of pain. If you were to accidentally swallow them, IF you don't burn holes in your GI tract, you will kill every bit of gut fauna you own. In the concentration that is used in Polar Pure, the crystals scar the hell out of most metals- think about what that means for your insides.