Re: 18-8/304/316/... SS fasteners?
I am certainly biased here, but I have been switching to titanium. It solves all the corrosion problems, and is much stronger than 300 series steel. Since fastener prices have started to come down, it is not nearly as bad as it used to be. Figure between 20 and 50% more than 316 stainless, the more commonly used sizes are cheaper regardless of size for fasteners typically.
Check the prices at McMaster Carr for type 2 or 5 titanium nuts and bolts. Type 5 is the go to for the Marine environment for its strength, but a lot of bits are only commonly available in type 2.
If McMaster doesn't have what you need let me know, our catalog covers fasteners from 1mm up to around 4 inches.