I also tried the magic mesh door, but I felt like I was always fighting with it to get in and out and to fold the sides in. I built a full length removable screen door with parts from Home depot. Screen frame sections are available and the screen material. There are also pre-made corners and of course the spline that holds the screen mesh in place. The hinges are in two parts and the door simply lifts off for travel .
I used a simple latch from the inside. The down side is you can't close and latch it from outside the camper. So we use it at night and only when we are inside. Foam weatherstripping seals out the bugs !