Building an RV-14 in Aus, they have the wiring harness. I am running the cables but will likely just use a hand held model, As Dave says, we don't require a fixed one.
If you do want the fixed one, depending on which state you're in, Dave Brown on here based in QLD, Horsham Aviation in Vic or contact the guys in serpentine WA. Probably others around but a good start for local people who should be able to help.