My girlfriend tells me the same story you do. She has many clients who are middle-aged, experienced, educated black professional or business people and are on the same page as you, but they all seem to be closeted when it comes to their political beliefs. Would there be any point, or would it be productive in any way, if you were to all band together into a black conservatives’ group online? As things are now, each one individually feels that it’s hard to stand up and make his views known because of the social pressure he’d receive, but perhaps together you would have more of a voice.
Do a quick google, and you'll find all sorts of black conservative and Republican groups on the web. There's a growing movement afoot of conservative blacks, though it's well below the radar right now.
I became curious about this myself some years back. When I looked around, I was surprised at all the black right-wingers I found.
But, unlike black left-wingers, blacks on the right don't individuate from the larger group. It's because we're the real "post-racial" folks.
As far as such groups being "productive", the only real reason for their existence is to spread the conservative message among blacks on the left. So, yes, they can be of benefit.