Have the 280ah cells been on Amazon before? Twice the price of our China direct sources, but an option for sure. Especially if you need a replacement?
Hopefully I copied this link ok.
https://www.amazon.com/gp/product/B08D7ZTPWJ/ref=cx_skuctr_share?smid=A1G45A0B8KQHYM
I noticed they show M4...