Chlorine tablets are cheap. They're available from farm supplies stores, usually for the folks who deal with stables.
Hellish things to store without any sublimation though, and they'll corrode anything metal.
Chlorine tablets are basically guaranteed to work. Every time. Something you can not know with the fancy new systems.
If you have a vacuum sealing/packaging machine, it is easy to seal them in so they last (almost) forever.
Edit: Heavily chlorinated water does not taste so good. After chlorination, boil it