Theres audience film from the November 16, 1978 (New York City) and November 28, 1978 (Buffalo) shows of It's Late. There both fragments of the song and the November 16th's quality is pretty rough, but the buffalo film is pretty decent for an audience shot film. There's no video from Hangman that I know of.
You can get the Buffalo footage in these DVDs along with other shows. Scroll down for the torrents. link
Not sure where to get the New York City film, sorry. Hopefully someone knows.