Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4154976.
UPDATE: I have replaced the file with a new version. The old one (which can still be seen in the pictures) did not work as well as I had hoped with a couple of unlocks. Not as many as before, but still too many. The new version printed well without supports, and I did not have a single unlock since using it.
ORIGINAL: I tend to carry a Fritz!Fon C5 in the pocket of my work pants so that I can be reached around the house. The older versions of the C5 worked well, I hardly had issues with the key lock. With the slightly newer version where the keys are a little more prominent, I have had issues with the key lock dropping a lot more easily.
I designed this sleeve to cover the keypad and especially protect the #-key which doubles as key lock key.