Long and short of it. My bathtub’s spring stopper has deteriorated. Building manager solution was to use a rubber stopper. I looked for a replacement part, couldn’t find one outside of an outright replacement. So I modeled and printed this one in TPU.
It works!
I printed a TPU gasket for a water bottle once a few years ago after my cat destroyed the original silicone one. Still works without any noticable leaks.