For the OP:
If you don't want to get a hard wired protector, you can always use the in-line (portable) one and keep it inside the camper. I had a 30 foot cord from this junction box. I simply cut it, attached a new plug on a much shorter cord, and then plugged in the protector. I stuck the other end of the protector out the hole of the trailer. No one is the wiser it's there, I don't forget it or loose it or misplace it this way, and it's always hooked up.
The remainder of the 30 foot cord, I purchased the opposite end plug and simply use it for an extension cord, or use it to plug in outside the camper. This way, if the protector ever gets zapped, or I needed to replace it, it's a very easy switch. Just unplug and move on. When I sell the camper (someday), I'll simply unplug the protector and keep it, then plug back in the original wire. No extra wiring to deal with. You can do the same with the 50 amp version too if you don't want to hard wire the permanent version in your camper.