This website by Scott K. Williams estimates 65,000 with 13,000 soldiers actually involved in combat.
http://www.usgennet.org/usa/mo/county/stlouis/blackcs.htm
Another site states "He also cited professor Edward Smith, director of American studies at American University, who has calculated that between 60,000 and 93,000 blacks served the Confederacy."
The 93,000 estimate could be looked at this way.
"210,000 (9.5%) African American. Half were freedmen who lived in the North, and half were ex-slaves from the South. They served under white officers in more than 160 "colored" regiments and in Federal regiments organized as the United States Colored Troops (USCT).[6] Joseph T. Glatthaar, Forged in Battle: The Civil War Alliance of Black Soldiers and White Officers"
Another newspaper article I found from the Athens Herald had a statistician who estimated the number to be 186,000 so to say 210,000 is probably correct. the 186,000 divided in half would be 93,000 and 105,000 would be half of the other estimate. The real goal then is to collect as many pensions as possible, newspaper articles etc and document from these sources. The Lillian Henderson Roster listed some and documented solders who were to help recruit and form Negro units. With some luck we can compile names, mark graves and document these soldiers for everyone to see.