The reason I ask is because I'd like to make sure I can get a legitimate 6p battery replacement from an official source. I would hate to replace my battery only to find out there are issues w/ the replacement..
Check with iFixit.
For one, they have terrific step-by-steps, and secondly, they sell batteries for some devices. I'd assume their stuff is good, or at least they truly believe it's been well-sourced.
I think in some cases, where they don't have batteries, I've seen tips on obtaining a (decent) one.
Most lithium batteries have been coming from companies you never heard of in China for a few years. And most of the ones you find in the shop here (Android Batteries - ShopAndroid ) or on Amazon are legitimate.