Drain strainer

Simple 40mm outer, 16mm inner, 0.5mm thick drain strainer. I use it in my tub to catch hair etc. while still being able to close the pop up plug. Given the many possible drain and plug designs your mileage may vary. Uploaded as STEP file, so feel free to customize as needed, although frankly you'd probably be quicker off to just redraw the thing.

I haven't tried it but probably best to print in something like TPU so it doesn't accidentally crack and fall in, although at this thickness PLA is more flexible as well.