Exhaust Hardware - Stainless Steel?

I was doing an oil change and a mech buddy saw a bit of gray soot on my firewall and suggested I remove the aft portion of my exhaust and clean and Mouse Milk the knuckle-joint area. In doing so I found out the hardware for the flexible knuckle joint was steel (cadmium plated), not stainless. My question is do I change to SS (which I think I should) and more importantly, where do I find the nuts and bolts and springs?

Thanks for any help