There Huawei HB5N1H and compatible batteries are working.
This model is a bit shorter and less wide but thicker than the original battery but it works just fine, if you fix it with a spacer.
Batteries that are used and reported to be working are the ones from
(this list must not be complete of course; they are just the one’s I remember).
a friend of mine gave me his old FP1 including 2 spare batteries, which I actually don’t use at all. I would be glad, if they could be of use to someone else. If you want, I could send you one to Lüneburg or Berlin.
I just don’t know how much power they still have in them