So 1 12mm x 35 x 1.75 button head cap screw grade 8, blue loctite and a washer. Cant really imagine why it would be 12mm screw, a 10 would have been more than adequate in my mind but that's Guzzi. Weight, what is this thing weight
I wouldnt worry about the snoring washer if you cant source one, a plain one with the loctite will be fine.
Ciao