4 out of 5 end caps have startet to fail on our caravan, and not only are the replacements expensive, but they're badly designed. They don't fit very well, and rely on a screw through a lose metal plate to stay on. Now I've lost one of my end caps completely so I have made a click-on replacement instead. To mount it, insert bottom part first and apply gentle violence to top part in order to click on. This is as designed, as I want it to stay there :-) I took a small piece of wood and a hammer to push it into place. Obviously you can just mirror the part for a left version.

I have not designed a replacement for the left end cap next to the door. It's a different design, that works much better than the original.

Pictures included of both the original part and my replacement.

Print vertical as designed for strength. I used 0,10mm layers and a 0,4nozzle - and supports everywhere.