Vehicle (Motorcycle) Sale without ZB 1

Hello Together, I (private) would like to sell my motorcycle to private. Unfortunately, a few months ago I got the registration certificate Part 1 (vehicle license) and can not find it any more at all. What can I do to make the change notification as easy as possible for the buyer. Is a change notification possible without ZB 1 at all? I researched something on the Internet and could only find special cases and some mot Swiss Federal Declaration of Loss. all: I am just abroad for 6 months and my father would take over the sale. I have already signed a pre-filled (purchase) contract before I am abroad. That means an official course with new application of the ZB 1 is unfortunately not possible for me… How can I sell my motorcycle now best for the buyer? Already have interested parties. I give the vehicle letters with the entire previous owner history and the HU/AU examination of course. t and still has TÜV until April. Thank you very much already and VG