@jpm @xssfox aha! I think I might have found it. That last one was the help -- searching on RS components for a 1.2mm pitch 3-pin connector and it's a Molex Pico-Ezmate apparently. https://au.rs-online.com/web/p/pcb-headers/7000824P
Challenge now might be to find 402025 150mAh batteries with this connector already installed
@nonspecialist @xssfox AliExpress gotchu fam. Contact these folks and see if they can do a special order run using this connector and the wiring polarity you need.
@nonspecialist @xssfox at the very least, as someone else has suggested, you can just buy these pigtails directly and attach them to the cells yourself.