+1 on Ace Hardware, or the equivalent in your area. Stainless and chrome in all sizes. I started replacing all of my bolts with chrome, then switched to stainless when the chrome bolts started to show some rust.
All of that hardware is still available from your Honda dealer.
Quite a bit of it is, but not "all" of it; shock mount and exhaust mount bolts are no longer available, for example. Nor are the triple tree clamp bolts (10x35) or any of the engine hanger bolts.
Go to Bike Bandit and do a search for what you need; they're the best gauge (I've found) of what's available. They only list stuff there that is still available from Honda, and they have most of it in their inventory. If you see it listed, you can then go to your dealer and order it for a little cheaper (though one thing to note is that most of these bolts are merely zinc plated and are not likely to last any longer than the originals).
Otherwise, try Ace, or someplace like it. Home Depot is oddly limited in its bolt selection, but you can look there, as well. As others have pointed out, approximately 99% of the bolts on a 550 have a 1.25 pitch. Keep this in mind when bolt hunting.
You could get all of your old bolts re-chromed, but at $4 a bolt, this is a more economical way to go, and those old bolts will re-rust eventually, anyway.
All nuts and bolts from Ace Hardware:
Hope this helps
Ron