Battery replacement 2017 MacBook Air

The only way to get an official Apple OEM battery is by having an Apple Store or an Apple Authorized Service Provider to replace the battery for you.

FYI, if you ever need to have the battery replaced later on once Apple no longer supports this laptop, then you can get a third party battery from OWC or iFixIt (these are the only third party vendors I would trust, but I have had bad batteries from them over the years). Both vendors even provide a kit with the necessary drivers to do the repair. For a 2017 and earlier MBAir, it is very easy to replace the battery (no glue, it is screwed in) with the hardest part of the process being disconnecting the battery connector from the Logic Board (sometimes it is very tight).

Refer to Battery Service in Mac Repair & Service - Apple Support. If an Apple Store is not convenient for you, you may be able to send it in. Ask.

You may also want to review Self Service Repair - Apple Support but do consider any other alternatives unless you have literally no other.