Do you have any specific fasteners in mind, or just all of them?
Stainless socket cap screw kits were popular to replace the cheap cheese metal crosshead screws that were prevalent on Japanese machines 20, 30, 40 years ago but the fasteners on more recent machines are better quality. So these sets are not so common now - although there are kits for those who think blue anodised looks classy!
I'm lucky to live near Namrick (
www.namrick.co.uk ) so can buy screws individually without having to pay postage.
If we were to list the various sizes (diameter, length and thread pitch) for various sections of the bike (engine cases, handlebar screws, brake hose clamps, brake callipers, chain adjusters, sidestand switch etc) and then we can order them in sets ourselves from whoever works out cheapest.
Perhaps we can assemble a list of all the fasteners sizes - as we take bits off we measure the various screws, bolts etc and report them here to build a database.
I have systematically replaced all the fasteners on my 1970s Moto Guzzi with stainless over the years I've owned it (20+ now) - I have had some discussions on tensile strengths and have found A4 stainless to be fine where they are just holding things together such as rocker boxes, engine cases, chassis parts and even brake callipers.