The quest for primary sources can often start from reading a good academic book on your topic. In addition to the sources listed below, you may find others of interest by checking the footnotes, endnotes and bibliography of a published secondary source.
Digital collection of Alternative and Underground Press publications focused on Vietnam, women's rights, sexual liberation and civil rights in Britain and America. 1962-1977
Oral history interviews with more than 2,600 historically significant African Americans in fields such as the arts, business, education, entertainment, the law, the military, politics, religion, and science.
Princeton University Library has a number of collections of manuscripts that reflect African American history. You may search the list of Finding Aids at https://findingaids.princeton.edu/.
Some collections of note include: