I bumped into this one while running around, for about $64.00 you could throw one of these in your BOB (if you live near the ocean or going on any boat cruises)in the event salt water is your only source for water.

I had bought PUR Survivor 35 Water maker awhile back since I live near the ocean and lugging it around is definitely a pain (8 lbs). I know you can get a lot of military surplus from e-bay from time to time, the one I bought (PUR 35) was normally $1,895.00 new, and I got it off of e-bay for $200. It had never been used and still had biocide in it with the military annual inspections. Tried it out in Daytona Beach and it worked like a champ. Heavy thing though, but if I went on a boat cruise I would be interested in the Sea Pack. (Easy storage, light weight and very versatile)

Sea Pack