Whatever you end up with make sure it's 316 grade stainless. And as per previous post, be meticulous with your reassembly.
Ensure all bolts and the threaded areas they are going into are clear of existing corrosion and contaminants (I run a tap & die through threads and blast with brake cleaner).
Run Loctite or anti-seize on everything (refer to Yamaha factory manual for advice to run what on where - manuals can be downloaded from the 'net).
I may be lucky but my local fastener supplier has always been happy to fix me up bolt-by-bolt in the past when I've wandered in with a bag of bolts or a small list. I always try to go when I know they are quiet and I am not holding up 10 other customers.