If the camera being centered on the rear wall is not a requirement, see if there is a cavity between your shower enclosure and the bathroom wall to run the wiring.
I installed the same camera and love it--good image and turns on and off same as the tailgate camera. My Lance 1050s has a plumbing chase between the shower and the rear door--I simply drilled through the rear wall into the chase, ran the wire down below the shower and forward to the left front corner of the camper. Lance emailed a diagram of the rear wall. The camera is mounted above and just to the left of the rear door. It is not far enough off center to be an issue, especially since the camera does not have the centering lines provided by Ford's tailgate camera.
I also purchased an additional 16 feet of cable which I connected to the tailgate plug harness and permanently mounted under the truck, routing it to the left front corner of the bed, placing the camera connection at the same location as the camper connection.
