Someone on the VSG mailing list suggested that this film from 1970 had some great footage of the Sài Gòn of the day. It somewhat complements Balaban's Remembering Heaven's Face, including a recording of Ông Đạo Dừa (the coconut monk) and his followers performing their pan-religious ceremonies. John Steinbeck IV gets a lot of time to sound like some kind of hard-arsed hippy, labelling voodoo and suchlike the "psychic sciences".
There are probably more gems to be dug out of the Canadian National Film Board website.