Since official Apple Stores typically do not service the iPhone 4 anymore, you will need to rely on independent retailers:
National or local battery specialty stores often carry "compatible" versions for older models. ⚠️ Critical Purchase Considerations buy iphone 4 battery locally
If you plan to install it yourself, you will need specific tools often sold in "Fix Kits": Since official Apple Stores typically do not service
A successful swap can restore the phone's ability to hold a charge for basic tasks like music or nostalgia, sometimes lasting up to 2 days on standby. How To: Replace the iPhone 4's Battery in 2 Minutes The iPhone 4S battery has a connector on
Ensure you buy a battery specifically for the iPhone 4 . The iPhone 4S battery has a connector on the opposite side and is not compatible.
Local shops may charge a small service fee, but some may refuse the job due to the risk of damaging aged internal ribbons.