How do I replace the battery?

After a couple years fairly constant use my battery it worn down such that it only lasts about 20 minutes before needing a charge, so I am also looking to replace it myself, could someone please give me a link to the EXACT replacement battery to buy and any pointers they have for doing the task? In the specs it says "Li-ion 65 mAh", but after opening it up I see it's an arc shaped battery with "GREPOW YE2514246 3.7V 60mAh 0.222Wh" written on the underside, I could really use help finding such a specific battery!