Wal-mart does have it. The people there are dumb, don't believe them. Look for the Culligan(sp) water dispenser with the big big jugs, you buy the jug the first time, i think like 6 bucks, you get the first fill free, and after that, you just buy refills.
If you read on the machine, it says reverse osmosis and deionized.
"by a wonderful method of filtration called reverse osmosis, it is then deionized blah blah blah"
that kinda stuff. Believe me, they have it.