We don't have anything to do with replacing parts on iPhone. "We" are all users on this user to user only forum. Apple isn't here.
Apple has NEVER made iPhone a DIY repairable device. Likely because most users don't have the ability to replace parts in electronic devices AND because the devices water resistance would likely be destroyed by users trying to replace parts.
Apple also does NOT sell parts to individuals. The smartest, safest, wisest thing to do is take a phone needing a new battery to Apple for replacement. It's not expensive. It will be replaced with authentic parts. It will come with a guarantee.