Hi KKN,
Each XMSirius head unit has it's own unique Electronic Serial Number which is linked to the owner's account (read: credit card number). You will have to buy your own head unit and set up an account with XMSirius. Maybe take a photo of the existing mount in your coach to a store like Best Buy that has a complete selection of receivers. You can then purchase the head unit that fits your mount.
-Cam