https://www.aliexpress.com/item/3298...56944c4dZhPXEn
The new battery I bought is a bit smaller. Just a bit. So I needed to stick it in with blue-tack.
There are other batteries too, go to google. Use this as a search string.
site:
www.aliexpress.com battery onyx boox m92
I got ...
https://www.google.com/search?source...4dUDCAU&uact=5
Whatever.
So far, it seems to have good life. Obviously, I haven't exhausted it, and re-charged it.
See what happens.