i'm also looking for a black piano hionge but I can't find it anywhere. I'm not sure how paint would adhere to that though with all the movement...
I had the same problem ... ended up buying brass (was on sale), then roughed it up a bit with with wire brush attachment on the dremel, wiped it down, then primed and finished with spray paint. I kept the coats very light and moved the hinge after each coat. No problems to date, but then I haven't opened any of those panels much.
Cheers.