Echo the "more hassel than it worth" sentiment. I've seen it tear into gear worse than iodine tablets that aren't properly sealed. Between that and it's general reactivity, I don't bother with it any more.

I haven't read anything about being a tested water purifier, but I can't imagine that it isn't. All of your strong oxidizers (chlroine, iodine, hydrogen peroxide) attack stuff at the cellular level, so I would hazard a guess that potassium permangenate SHOULD work. It's the dosing that is tricky.

I suppose, if you REALLY have your heart set on it, looking your phone book for a chemical supply house, or hit one of the academic chemical supply houses online. Or eBay.