Thank!Lots of info in the DIY lifepo4 battery section. This is the 'Beginner Friendly, Plug and Play" section which is geared towards drop in replacements like the Battleborn.
Will recommends CALB and Fortune cells on his website, as well as blue aluminum cells sold through BLS. If you want the best bargain the blue Aluminum cells sold through Xuba and Xaomi are popular with a lot of people here (same cells different sellers). Spend some time browsing through the DIY lifepo4 section I linked to above.