The handle has 4mm*5.7 holes for M4 screws or threaded inserts + M3 screws. I did it with
https://www.ruthex.de/collections/gewindeeinsatze/products/ruthex-gewindeeinsatz-m3-100-stuck-rx-m3x5-7-messing-gewindebuchsen
which holds pretty strongly.
If you need different holes, I also added step and f3d files for easy modification.
Size: 136mm * 11mm * 27mm