Hi Peak_man,
Thank you for reaching Microsoft Community.
Replacement for the earbuds are sold by pair. We really don't support replacement earbuds from a third party vendor. I would recommend to contact our live support team to process a replacement for your Surface earbuds. You may reach them through the numbers listed in Global Customer Service phone numbers (microsoft.com) under For Business users. This also works with Home users , just select Surface then Home as a type of user in the IVR prompt. You may also reach them through this page: Contact - Microsoft Support.
Kind regards,
Lavenia