Reverse camera switch?

I've searched, and I've looked through the posts I've found, but I haven't found anyone who's made this simplified mod. I'd like to wire in a basic, 2-position switch, with one position being normal operation, and the other being the reverse camera on constantly.

Based on what I can decipher from the turn-signal camera mod posts, I suspect that this is achievable without too much trouble, just by having one of the switch positions provide constant power to the reverse trigger wire that goes into the HU. But - I can't figure out which wire that is, or how much power to use, and I'm scared of melting the HU down if I get it wrong. I would be eternally grateful to anyone who could point me at the right way to do this.

 

@cproaudio, would it be possible to incorporate this as part of your turn-signal mod kit? Or would you be willing to sell a separate kit to do just this mod?