How to split off the camera signal for a second display?

I have on order a heads up display (Hudway Drive), which can accept a video signal to display when the car is in reverse. My 2019 SL already has a backup camera, so ideally tapping or otherwise accessing the composite video feed to connect to the HUD would be perfect.

I did some searching and I can find a lot of 3rd party wiring harnesses for use when replacing the head unit, but as far as I can tell they won't work in my situation because I would like to maintain the signal into the headunit as well.

Is this possible? Does anyone know what wire I would need to tap, or an existing harness which I could add to duplicate the composite signal?

Yes, it's in the service & repair manual.

There are 4 pins that run from the back of the car into the center console. I forget offhand, but they are Power, ground, camera signal, camera sense (present), IFIRC. There's also a shield to prevent interference. The camera sense is grounded if the camera is present, and the others are as you expect.

These wires run through the hatch harness, through the left side harness, down behind the rear seat in the rear pillar to the floor, through the floor to the compartment at the base of the A pillar (at the floor), through the dashboard, and to the center console. You could tap into these pins anywhere along the way for your second monitor. You're really going to want the service and repair manual if you're going to do this, and the camera signal is analog, which means that if you draw down the voltage too much or add interference, you will affect the picture quality.

Good luck!