lid.stl was my first "fancy" attempt, with a hollow bottom and print support ribs, but I had issues with the overhangs when printing. lid_flat.stl was a revision with just a flat bottom, and works just as well for its intended purpose, and prints mush faster with a low infill amount.

I made this using a rotate-extrude in openscad based on a profile drawn in Inkscape and exported as a dxf.