@bsrg

There are only 2 solutions:

1 - Contact Mika Rottenberg and try to find out if she still has a copy of this film.

instagram.com/mikarottenberg/

2 - There are groups dedicated to the discovery of Lost Medias, such as these here:

reddit.com/r/lostmedia/?rdt=44688

lostmediawiki.com/Home