Here is the company I have delt with
RV Water Filter Store: Standard Filter Canisters for Whole RV
They can be found in the outdoor Yuma market and right now at the FMCA rally here in Indio.
I bought the 2 membrane unit for about $550.00. It sits outside my coach and fills the main water tank. I then use the pump and run everything with RO. Nice to drink from the tap.
I can make 1/2 a tank in about 6-8 hours (5 gall in 45 minutes). When I need to fill I just turn on the campground water supply and that turns on the unit. When full I turn the water off and the RO system quits.
I also use it at home for 5 gal jugs of drinking water.
I didn't install it in the coach since I must winterize in the fall.
Hope that helps.