Two Reverse Cameras To One Camera Input

I want to setup a second reverse camera on the back of my enclosed trailer and have a SPDT (on-off-on) switch on the dash that allows me to select between camera 1 and camera 2. I have done some testing so I know that I can run the video signal for both cameras through an RCA Y adapter and everything is fine as long as only one camera has power at any given time. The problem is that the stereo camera trigger wire needs to receive +12V when a camera is active which means that the trigger wire must be connected to both cameras. I am trying to determine how to send the signal to the trigger wire without back feeding power to the other side of the switch and then to the other camera. I'm not concerned about either camera coming on with the reverse lights, that is more of an annoyance to me, I'd prefer to manually activate the desired camera. The best idea I can think is as follows. +12V to SPDT switch, output 1 from switch to camera 1 and to + side of coil on SPST Relay 1, output (87) from R1 to steres trigger wire. Same setup for second camera and relay. This means that both relays have terminal 87 connected to the same stereo input wire, thus power is back fed when the relay is at rest. Will this back feed cause the relay to activate (close) thereby allowing back feed to the other camera? I'm sure I'm not the first to try this so if others have better ideas I'd appreciate all input. BTW, if it helps, the stereo I'm connecting to is a Pioneer AVH-X3600BHS which only has one camera input.

Use 2 diodes. Banded ends connect to the reverse wire of the deck. Other ends, one to each of the camera power wires. https://www.the12volt.com/diodes/diodes.aspLet's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB

I thought about diodes, just don’t know much about them. Did a quick search and learned that there are several different kinds/ratings. I did a bench teat with the relays this evening and that worked. Might do some more research on diodes and experiment with that also.

Probably easiest solution would be DPDT switch, with the power to camera and stereo sensor wire isolated but I can’t find a Dpdt switch to fit the small round spot in my dash.

There is absolutely no current draw on the deck's purple/white wire. Pretty much any diode will work. Look for a 1N4001 or any number between and including a 1N4007Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB