filamentworld Standard PLA PLA
Grind the front
Make the surface a little bit smooth for a nice look fitting to your 19" rack.
Drill two holes and take a self cutting screw to fix the raspi on the mount.
Insert the card holder in the frontplate and it should fit very strong. If required grind it for a smoother insertation, but if it is too loose you have to glue it to be fixed.