I would not change these for chromed ones, even if you could find some. Chrome plated high strength fasteners can suffer from "Hydrogen Embrittlement", and break easily. Hydrogen embrittlement is pretty common if high strength steels are electroplated without the very stringent process controls necessary to prevent it. Chrome platers interested in chroming for looks are not likely to even know about it.
Under NO circumstances should you change them out for Stainless Steel! Stainless would have about 50% of the strength of the stock bolts. Brakes are critical, so maybe just clean and paint with a good aluminum paint?