So it came to be that mouse's dongle had..... unfortunate accident. Electronics were salvageable and repairable but the case, sadly, was not. So I made one - sturdy and simple with same properties as original (fits in original recess)
Printed with PET-G @ 0,1 resolution for better looks. Should look even better printed with transparent resin. I had to use brim with part B since adhesion surface is minimal.

For those who'd like to tinker with it a bit, I added 123D file for 123Design program.
Yes, know it is outdated ad basically abadonware but still good enough and simple enough for me and does not require fancy accounts God knows where.