This is a bit tighter fitting cover for Fotek SSR than the one I tried. This version might not fit if your printer does not produce dimensionally accurate prints. YMMV.
When printed with PETG infill can as low as 25%. I use KISSlicer so again YMMV if using some other slicer. The symbols are 0.4 mm thick and I printed mine using 0.2 mm layers, symbols with white filament and rest in black. On single nozzle setup it required changing filament only twice: black-white-black.
There are 2 versions, with and without the symbols.