In the May 1995 issue of America's Civil War there is an article entitled: Driving Dixie Down, the Fall of Richmond. In this article on page 41, it states: On March 29 there was a parade of two newly formed black volunteer (Confederate) companies and three companies of convalescent white troops in Capitol Square. Since there were no uniforms available for them, it was not a very stirring display. But President Davis was probably too busy to notice. (This was after the EP.)
I am told a company is comprised of 100 men so this documents 200 black volunteers.
If anyone can find any more, please post. There are so many conflicting opinions, it would be interesting to see how many we could find.