i had the same unit you do and was going to get this one... but i just bought a new RODI unit last week and its a low pressure unit so i dont need it anymore...
They're sold separately I believe, but I bought mine as a bundle. Wouldn't hurt to add a sediment filter in front of the pump as well, it's about $10 or less.
I'd have to know a little bit more about the details of how you want to use it, etc. Just installed a 300 gpd RODI at a public aquarium a couple months ago.