The idea is simple - just print the 2 parts.
The first insert screws into a 20 mm hole that you drill into the top of the empty container.
I would recommend to glue it in with some super glue or 5 minute epoxy to secure and seal the fit.
Second part is a screw that seals the deal after refilling - done.
Threads are designed in a way that it should work even with a not perferctly dialed in printer.
If you have any makes / issues / improvement ideas please let me know.
The author hasn't provided the model origin yet.