Very, very tough stuff. Every time one of them make the HOF collectors have kittens trying to find something. Some of them have no career-contemporary ("CC") cards or only a card or two and they are obscure or rare.
Charley Burley: no known CC cards
Lloyd Marshall: 1940-70 Boxing News (UK)
Holman Williams: 1946-47 Propagandas Montiel (Cuba), plus a RPPC I have.
Herbert "Cocoa Kid" Lewis Hardwick: no known CC cards
Jack Chase: no known CC cards
Eddie Booker: no known CC cards
Aaron Wade: no known CC cards
Bert Lytell: no known CC cards
Absent cards, I go with publicity photos. Those do exist for the Cocoa Kid, Booker, Marshall and Burley. Perhaps for the others, I just haven't chased them.