SEARCHING FOR SUGAR MAN An astonishing rock documentary that seems pure urban legend. Sixto Rodriguez (below), a folk singer from Detroit, recorded two early-’70s albums that went nowhere in the United States and made him a mysterious superstar in South Africa. Malik Bendjelloul’s film follows the efforts of two fans to find out whether he’s still alive. Magical. Extras: making-of featurette, interview with Rodriguez and Bendjelloul (Sony, $30.99; Blu-ray, $35.99)