Signup with Missing Domain Extension
From Lunarpages Web Hosting Wiki
I have a domain extension that is not in your drop down. What do I do?
If you already own the domain with an extension that is not listed, or the signup says it is an invalid domain, please choose the .other extension to sign up.
Once your account is approved and you receive the account information, please email email@example.com with your correct domain and they can change this for you.