I did my own research, lol Chlorine Dioxide is the best chemical to clean water in a pinch. Don't confuse it with cheaper Chlorine tablets.
- Could not find any with a sane price anywhere in AU.
- Iodine based are banned in EU.
- "Ef-Chlor" you get on Amazon is Sodium dichloroisocyanurate (NaDCC), is not Chlorine Dioxide. Wiki
- Water purification tablets
May The Force Be With You.
Make your own with Sodium Chlorite + Hydrochloric Acid.
PM if you need the details.