Need help tapping into the reverse light

Hi everyone,

I'm installing a rear view mirror mounted backup camera on my 2013 prius C.

I have successfully tapped into the fuse box for power and got the camera cabling done already.

The only thing that I have left is to tap into the back-up light cable so the camera turns on automatically when I put the car in reverse.

I need help identifying where I can tap into the reverse cable inside the interior, as I have the positive wire from camera running from the trunk door into the interior.