This isn't specific to repair shops, but there are a plethora of 3rd party battery options for many, many cell phones. iPhone included. Even stuff sold from com

This isn't specific to repair shops, but there are a plethora of 3rd party battery options for many, many cell phones. iPhone included. Even stuff sold from companies like ifixit. My experience with replacing those batteries with anything except the OEM battery has been always .. let's just say underwhelming. Maybe I've just been consistently unlucky, but there doesn't seem to be any quality control and plenty of outright lying from 3rd party vendors on battery capacity and expected performance on aftermarket cells.