I want to add a entry door in the rear wall of our 5th wheel

Are you parking it permanently or will you move it regularly? If permanent I would get a regular house patio door. If you are mobile I would think you would want a RV type door. If the latter I would try some of the RV salvage places around Elkhart, IN. or White Pigeon, MI. There are several in the area and you are not too far away so you might want to take a trip and see what you can find.