Those look very similar to kind I'm currently looking for. Apparently a certain Solo cup fits perfectly. The smaller kind you use for mouthwash almost. Very difficult caps to find in decent condition.
That being said, I just helped set up a 3D printer today and plan on printing my own. If and when I get to that point I will keep you updated.
Well if you end up going the 3D printer route and need one in good condition as a model I have three of them on my car in great shape. I'd happily lend one to you.