Do you know of a good source of calcium hypochlorite?
I understand that what is used for pools is often recommended against because it contains other substances that would make it not recommended for treating drinking water.
Any local pool store should have it, also Ebay. One pound bag should last you a very long time. It usually comes in a plastic bag. You need to transfer it to something more suitable> I place mine in a mylar bag and then placed it in a used plastic coffee can. Gloves and mask are a must when handling.
Here’s a good article on it:
http://www.emergencyhomepreparation.org/viewtopic.php?f=25&t=97