You need tanks in a van mount, I use anything that holds water with a tap in my static shed(ie a water butt or s/hand cylinder-my last one had contentrated curry, it cleaned out ok.
I think you only need 2 stage RO if you dont want to drink the water the 2nd one of a 3 stage will act as a pre sediment filter as well .Look under water treatment in YP for a local supplier or use a link to any of the firms on the board.
I built my own, but you coild buy a complete wfp system from a grand or so.