I would not be surprised if they are mild steel. You could try painting
them, but you will probably be fighting a losing battle. On the other hand, stainless hardware does not come cheaply, so you might prefer to remove your hardware every once in a while and repaint/re-coat.
I'm running out the door so I don't have time to do too much checking, but here are a few possibilities from West Marine. A couple of notes:
1) I think I have seen the same style hardware as on the Boler/Scamp window cover in stainless, but did not have time to look for it just now.
2) You will note that WM shows the mfgr part number. Sometimes it pays to shop around as they can be quite a bit more expensive than other sources.
Sorry for the clumsy links; I don't have time right now to shorten them or to save/transfer photos of the hardware to this post. But at least this will give you some ideas for now. (And they may not all fit exactly.)