The Sparlock entry on Wikipedia is well written. A lack of sources appears to be a problem. I wonder if the recent news articles in Norwegian would qualify. If they have to be in English, maybe a Norwegian Sparlock page could be set up and it could be translated into English.
It would be nice to use the video itself as a source. I don't think Youtube videos qualify. It should eventually be available on JW.org (assuming the Watchtower Society isn't too embarrassed to post it). I also checked the Library of Congress and couldn't find it, but there are some othe Watchtower publications.