How can I get a replacement AirPod?

See the following from How to find your lost AirPods - Apple Support

Replace a missing AirPod or case

If you still can't find your AirPod or Charging Case, or if something is damaged, get the serial number and then contact Apple Support for a replacement. Then learn how to set up your replacement.

You can also learn more about AirPod pricing and service options.

Hello, you can make an appointment though the Apple support app or on Apple’s website. This is the Apple support website link, Official Apple Support.