I got this from a friend several years ago, but have never used it. It's no longer in production, but it still highly regarded as lightweight water purifier (see links). Use salt and electricity to chlorinate your water. Used by the US military! Retail price was about $150, but it is no longer produced, so hard to find. Needs 2 lithium CR123 batteries, which are about $15 on Amazon. https://www.rei.com/product/709012/msr-miox-water-purifier https://www.trailspace.com/gear/msr/miox/ https://www.waterworld.com/technologies/article/16206636/us-military-places-order-for-msr-miox-purifiers-to-destroy-pathogens-in-drinking-water