Thanks to Smakx dingoonity user has found this listing that claims to be a 2100mAh, which would be the highest capacity that I have seen in a BL-5B:
https://www.aliexpress.com/item/HSABAT-BL-5B-3500mAh-Battery-for-Nokia-3230-5070-5140-5200-5300-5500-6020-6021-6060/32813119218.html
