you can try avo... they make a w/a kit in the rav4 turbo kits and tghey are a pretty good set up... very small piping involved and they are very efficient...
but if you wanna make your own you need to get a cooler to suit then weld plates on it where the water can be stored... you godda get a pump of some sort.. i hear they use boat bilge pumps then they feed the air to a oil cooler to the front then feeds into the intercooler and it cycles around like that.. i am not sure if they use water from the engine or they have seperate reservewire but that is meant to be a very good set up.. they tested that setup on wrx's and it showed to be around 30% more efficient in cooling then a 1ggte size a/a cooler