Water to Go? Like a faucet + a water bottle? Jk, i think most of us just use the water the that we are given or mess around with our pH, salinity, and minerals our selves. Lots of people buy RO water from stores in their area...I have not heard about people buying water over the ol' interwebs.
-Sometimes I feel like I'm up beer creek without a pint glass-
Water To Go is who I use exclusively when I buy RO water. There is a store a few miles from my house and their RO setup is impressive. I have been very happy using them. The store near me has a deal where it's cheaper if you buy 100 gallons (in credit) at a time.
Naturally, since there is no minerals in the water, I add salts or mix filtered tap water to achieve a desired mineral profile.