Check your automotive supplier. The best one I found I think is called "No-Mar" or something like that. It seams to match well with most semi-gloss to flat black finishes. It comes in a spray can however so I don't know how handy this will be.
black touchup paint?
Isn't the black finish on most black audio equipment anodized, thus hard to match with paint? The shade varies by manufacturer, no doubt. Experimenting, I tried a Marks-a-Lot, too shiny (and tending toward purple, really). Wouldn't mind trying a spray, but small touch-ups are really the thrust of this question. Has anyone found a good solution? A dedicated "touch up marker" for audio gear would be mighty nice, if it were possible. Nothing would look exactly like new, but an improvement over a glaring scratch on the handle of my amp would be welcome.