Ugly but effective
This version is inspired on other 3d printers and mirror clip adaptations. This one is for Prusai3 - MK2 + Ikea Mirror
Just print three "mirror holders" and one last "mirror pusher" wich is actually pushing the mirror to the other three corners.
Fighting with the idea of using those metal black clips, I saw, there was a quite simple solution,
Pros: I have been working with it and it didn't fall down, or broke, it continue working even when it looks really bad... Base stays quite stable, does not move at all, but because the force piece (the one wich is doing the job) it is a bit big, a bit brute. But of course, the file can be modified to adapt better other optiions
Measurement is down to 0.1 mm, it fits with the regular MK2 and Ikea mirror.
It require to change the endstops on X and Y to make a small sacrifice of the printing surface. it is down to 18.5
(Do whatefs you need, I did this one long time ago... based on some file I cannot find at Thingiverse at the moment, if you see it... I give the credit of the idea and I write it here... I lost the search, or file.. I didn't changed the shape of the corner.)