
I opted to go for the tried and true water filter based design, as it seems to be the most prevalent and is relatively cheap to build yourself - there are pre-built models available from several homebrewing sites as well as places like Amazon and eBay for about $100, but you can build one yourself much cheaper.
I opted to go for an all-stainless (save the filter housing) design, because stainless. Many of these parts are available in brass/plastic (nylon or PVC) versions as well for less. The design I chose uses a Ball Lock post on one side and a disconnect on the other so I can easily daisy-chain the Randall into my system without having to mess with anything, but there are other options as well if you look around.
Check out the build after the break.