sprig_cover.f3d is the Fusion 360 file for the back cover. The back covers can be secured with M2 x 10mm screws and hex nuts.
If you choose to fabricate the back covers using a laser cutter, you'll need 2 pieces which are sprig_cover--dpad.dxf and sprig_cover--solid.dxf. One piece has a d-pad cutout for the buttons. It's designed to be cut out of 1/8" or 3mm acrylic.
To fabricate the back covers using a 3D printer, you'll need to print 2 of the sprig_cover--dpad.stl and 2 of the sprig_cover--solid.stl.