I needed a cover for a 250ml Pyrex beaker I got off of amazon, and I wanted it to be as air tight as possible. I couldn't find anything, so I made this thing. It has room for an o-ring, though I haven't sourced the exact one. I was planning to just make the o-rings with some silicone gasket maker or caulk.

This prints best on its side for me. I think it could be really nice with a resin printer too.