Feeling stupid here. I recently bought a 1947 SuperAlce. I decided to clean it up a bit and I wanted to make sure the oil tank was clean. It’s under the Fuel tank, inside the frame. I got it out by splitting the frame in two. The main top stud thread was damaged a bit, so I had it cleaned up. Now the trouble begins. 
The garage was reorganised and things were moved about and I can’t find this bolt anywhere. It’s in there somewhere, but I don’t know where! 
Would anyone know where to get another one? It’s part numbers: 31 and 32 in the attached diagram… The thread size is 14mm and it would be 200mm(?) long.
MG Superalce SA-Parts-Rotated-p51-p75_0001.jpg
I expect you will have to get a new one made. As soon as you do this, the original will turn up. 
I had to make a new 14mm bolt made for my Airone, as a previous owner had completely trashed the thread on the original. I’m not sure how the nut stayed on.
As above, it would probably be easier to make a new one than to try and find one for sale.
You could try googling Guzzi followed by the part number. It sometimes comes up with some useful results
Cheers chaps, I have been looking into having one made and you’re probably right, that when I get it made I’ll find the original.
Steve, many thanks for the link. I’ve had a look and ordered from the site, at least I’ll have something physical to try and fit.
I still feel so stupid?? 
You can try info@guzziretro.com Marco is the owner and he has most perts for Guzzi singles.
Cheers Phil