Brought this pump off Amazon to dispense washing detergent from a big 5L bottle.  Didn't fit, so made this adapter out of PLA.

Learnt how to model the threads using these links 

• https://hackaday.com/2020/07/12/learn-the-secrets-of-matching-bottle-cap-threads-to-one-another/
• https://www.noupoi.net/bottle-cap-thread-calculator.html
• https://www.printables.com/model/254386-shampoohair-carecosmetics-bottle-cap-24410