I was specifically looking for Professor Forstchen's doctoral thesis and ended up spending some time in the on-line catalogue of the Chicago Public Library. They have copies of all of these books and perhaps interlibrary loan can get them for you, but it can be difficult to get items from the Chicago Public Library, even when you live in Illinois. Some of these books are written by participants; some are recent.
A Regiment of Slaves: The 4th United States Colored Infantry, 1863-1866, by Edward G. Longacre
Eagles on Their Buttons: A Black Infantry Regiment in the Civil War by Versalle F. Washington (the 5th USCT, the first Black regiment from Ohio)
Strike the Blow: A Study of the Sixth Regiment of United States Colored Infantry by James Paradis
Record of the Services of the of the Seventh Regiment, U.S. Colored Troops, from September, 1863, to November, 1866, by Joseph Mark Califf
The 28th United States Colored Troops: Indiana's African-Americans Go to War, 1863-1865 by William R. Forstchen
The Black Civil War Soldiers of Illinois: The Story of the Twenty-Ninth U.S. Colored Infantry by Edward A. Miller
Illinois Freedom Fighters: A Civil War Saga of the 29th Infantry, United States Colored Troops by Dorothy L. Drinkard
Honor in Command: Lt. Freeman S. Bowley's Civil War Service in the 30th United States Colored Infantry by Freeman S. Bowley
Army Life in a Black Regiment by Thomas Wentworth Higginson (33rd Regiment USCT)
A Brief Sketch of the Organization and Services of the Fifty-Ninth Regiment of United States Colored Infantry, and Biographical Sketches by Robert Cowden
Some general titles that may offer more sources in the bibliography:
Forged in Battle: The Civil War Alliance of Black Soldiers and White Officers by Joseph T. Glatthaar
The Sable Arm: Black Troops in the Union Army, 1861-1865 by Dudley Taylor Cornish
I hope this is helpful.