I couldn't find any free print files for this, so I decided to try making one. It isn't perfect, but it fits on my wife's bottle just fine (hers broke and I didn't want to pay for a whole new cap haha).

I printed in PLA with tree supports and it needed minimal post processing. A little bit of sanding helps the edges to round out a little bit more. Fitting these on is somewhat a pain in the butt. I would like to do some editing on this to make it better but haven't had the time. If enough people are interested then I'd be happy to find the f3d file and post it as well for others to work on :)

***Update: Since my creating this, there has been another user who did a complete redesign that I have not yet tested, but heard it was easier to install. I think their design is just on printables but I am not certain.