My take on a housing for the GBxCart RW v1.2b. I don't know if this fits other hardware variants, as I only have the 1.2b version. It has a cutout for the switch and the ISP connector if you've installed that. There is a FreeCAD file attached so you can adjust / remix it to your needs.
Print Top.stl and Bottom.stl. You will need to flip Top.stl for proper printing. Best use clear material for the LEDs to shine through and print at <= 0.3mm layer height (I used 0.3mm). To connect the two parts, use two small screws or just glue the parts together.