Black rallye gauge

What black paint best matches the black on the rallye gauges? I am installing a voltmeter, and am going to use the gauge face with the numbers. It will fit with some modifications, but I need to fit a metal background to the gauge to fill in the area where the ammeter was. I have the metal to fabricate it, but apparently I don't have the correct black paint.

Thanks!
Maybe you could throw a couple of pics up showing your mod. I suspect others with a Rallye dash would be interested.......I know I am.