About 5 years back I copied all the Rainbow Quest tapes available on convenient Beta Video tapes. They are available through the Onondaga Public Library System so I assume they can be bought
I have Doc Watson with Fred Price and ??? Howard, The New Lost City Ramblers, The Late Great Grant Rogers, Tom Paxton, Judy Collins, Richard and Mimi farina, Sonnie and Brownie, John Hurt, Hedy West, The Clancys and Tommy Makem, a Puerto Rican band, Bernice Regan, and others. Being on Beta I haven't seen them in a while.
Don Meixner