I don't have any pictures but I mounted mine inside the car, then used a 3 foot trailer wire extension from there and keep that extension in the tray under the trunk floor. When I need to pull a trailer I just run the wire out the hatch and close the door on it.
Living up here in the north in salt country I've never been a fan of having the trailer electrical connector outside the vehicle. 99% of the time they aren't being used but are getting corroded to hell. Going on 3 years and I have yet to damage the extension by shutting the door on it (just make sure you don't run it where the latch comes down). If it eventually fails it's going to be a $10 part that needs to be replaced and will take me 30 seconds to do. I'd bet good money an external plug would fail because of corrosion long before my extension wire fails from repeatedly closing the hatch on it.
Let me understand this. You can buy some sort of extension with a flat wire that will allow you to leave the OEM part inside the car? Then when ready to use, plug this extension in the OEM harness and run the extension outside the car? won't the tailgate crush this extension when you close it?
Most local auto parts stores will have something similar in their trailer section.
I went so far as to take apart the OEM part that is supposed to bolt to the OEM hitch so I was left with just the plug to hide down in the spare tire bay. Then plug in your extension, run enough of it up into the under floor cargo tray and just pull it out when you want to use it. With the wire laid flat the trunk can close on it with no problem. There's a pretty big rubber weather strip there and it protects the wire. I usually put it about 6" to the left of the latch and depending if I'm towing my boat or snowmobile trailer leave a foot or 2 of wire hanging out of the Mo (one trailer has a longer whip than the other).