It was on
UbuWeb in its entirety for the last 12 months, however I've just checked the link & its currently down. There are however some other video bits to be found here:
http://www.ubu.com/film/sonicyouth.html
and the audio from it is available here:
http://www.ubu.com/sound/sonicyouth.html
as well as Thurston appearing on a Sonny Sharrock themed Space Ghost Coast to Coast here
http://www.ubu.com/film/sharrock_ghost.html
plus loads of other non-sonic related sonance.