It's just a simple Raspberry Pi 3 case that can be mounted using 4 screws to a flat surface.
The lid is press fit into the base.

I made this because I couldn't mount the Official case on my 3D printer enclosure. I'm using the Raspberry Pi 3 for Octoprint with my Creality CR-10.

UPDATE : I have uploaded the final STL files.

I printed the case in PLA and ABS (final product shown on images are PLA print), 15% infill. I suggest increasing the infill percentage to maybe 20-30% depending on the PLA.

(yes i know the texture/quality of the print is bit rough, it's due to imperfect bed-levelling and using a chemically defective PLA)

Final product shown on the images are printed at 0.28mm layer height. You may choose to print at a lower layer height to get a stronger bond between layers, specially in the thinner parts around the USB Type-A connectors.