I'm afraid I don't have any more information than was already reported here. There was a Made In Chicago PBS show in 1973, and to my knowledge it was on TV. It was, I believe, the predecessor show to Soundstage. The Soundstage video you see on Ebay is indeed from the 1979 appearance. There is no official release of it, and inquiries to PBS usually bring the response that they don't have the necessary permission (or maybe that it would cost too much?). That's it for PBS appearances. Lightfoot also appeared on Midnight Special twice and Saturday Night Live once. The latter will be available soon on DVD, in a new release of the SNL first season. I have information on that at my web site on the DVDs page (last item):
gordonlightfoot.com/GordonLightfootDVDs.shtml