Hello Ulf I wanted a seat a couple of years ago for my Daytona replica and resorted to making my own since my frame is a rigid one and I did not want the front end bent up as they are on swinging arm frames. Mine is made from 2mm aluminium sheet and welded where required then fixed to two rails for mounting points. A local man welded it up for me and it is quite rigid once completed.
I’ll try and get a photo tomorrow and send it to you or post on here if I can remember how. I have got a ‘Feridax’ type seat base which I got from a GSOC member who found an original and then had a number of copies made. His were made from sheet steel, laser cut and the base is quite heavy but extremely solid. The dimensions from this were used with minor changes to suit my frame. I then had to have a seat cover made to suit my seat base and found a local man to do it but that cost about £150 I think, including a foam base and fitting the cover.
I can take measurements and advise how I made mine if that helps or just ask if you need more.
Daytona Gold Star replica DBD34/Norton 996 Ducati Boposta 350 MV Augusta Aermacchi racer