So where do you get a pump like that? Can it run off the battery or do
you need to start the motor? I only need a couple of gallons a day.
Any ideas for budget DIYer's. I saw that one guys awsome setup who
posts here but I think it's a little ambitious for me.

That was probably me.

You really can't do it for less than around a Boatbuck ($1K). The basic
equipment remains pretty much the same from a single 24" membrane producing
5 gallons an hour to a double 40" like mine producing 35 gallons an hour.
It just takes more membranes and a larger pump. You can run a pump on 12V
but as Geoff has found you run into a practical limit of how much water you
can make. Even then you really need to be running the engine. A 1/4 HP
pump will draw 15 or more amps

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com