DesmoParts make s/steel and titanium fairing washers. US$15 a pair for stainless, US$25 for titanium - I bought 4 pairs for my 93 900SS (seat and fairing). Also sell complete body and engine kits containing stainless steel fitting and nylon washers. Bought a set of each and I'm slowly replacing the original bolts with stainless - being sure to use some anti-seize compound of course.
http://www.desmoparts.com/ducati/washer/washer.htm