In uk.d-i-y Adrian Caspersz wrote:
https://www.ifixit.com/

Bit of a premium, but wanted somewhere I could trust - the ebay/Amazon
sellers are awash with recycled offerings of questionable life. The £30
iPhone SE battery I got from ifixit has been installed for more than a
year, and whilst not original, it's holding charge well.

+1

At least with Samsung batteries, one thing to note is they only manufacture
the originals while the phone is in production. So, when I came to look for
a Galaxy Note 4 recently (made 2014), the 'Samsung' batteries on
ebay/Amazon/etc were all fake - all the genuine stock is long gone. Ifixit
didn't have one, so I ended up with a Ravpower from Amazon. Ravpower are
one of those made-for-selling-on-Amazon brands, like Anker, Aukey, etc and
their products are generally OK (not as good as Anker, but not trash).
It's been fine, but I don't use it regularly so it's hard to tell long term.

The moral of this story is sometimes a non-OEM battery is better than a
'genuine' one.

Theo