This is what I installed ...
https://www.amazon.com/gp/product/B010XWNFOM/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
The "lighter plug-in" monitor receives the signal wirelessly, simply needs to be "paired" with the camera !! My total rig is 60' long, and the signal is strong and has never wavered !!
That's the same unit I bought, and it won't connect from the cab of my truck to the camera. It's a common issue with large toy haulers. My 4250 is 43' 6", pulled behind a Megacab Ram 3500 DRW, that's a lot of aluminum between the camera and display.