Hi Kevin
Key's are not a user replaceable part on an Eigenharp, taking one apart and replacing the key assembly requires re-calibration which needs specialist software and a calibration jig. It's not something that you can do at home, which is why we do not sell key components as spare parts. Could you send us a picture of the damaged key? We may be able to assess the damage using that a little more accurately, otherwise your best bet is to send it back to us for assessment. We will have a look at it for you at no cost to you and give you an estimate for repair. You will need to cover the return shipping if you do not want it repaired and would like us to send it back to you.
You can always send email to the 'customerservices' address at eigenlabs.com, or use the contact form here: http://www.eigenlabs.com/supportcontact/
John