I am trying to find a copy to rent or purchase of a film titled "Star
Spangled Banner" directed by Roger Flint and which won a 1971 Cannes
special prize for short films.

I did a quick check of the Internet Movie Database which lists the
movie but does not show it as available for purchase.  You might want
to contact the Academy of Motion Picture Arts and Sciences or the
Cannes Festival to see if they could put you in touch with Roger Flint
or his agent.  You might be able to obtain a copy from him.  Good
luck.

Academy Foundation
8949 Wilshire Boulevard
Beverly Hills, CA 90211-1972 
Phone: 310-247-3000
Fax: 310-859-9351 or 310-859-9619
E-mail: ampas@oscars.org 

Festival de Cannes - Film department
3, rue Amélie - 75 007 Paris - France
Phone: 33 (0)1 53 59 61 71 
Fax: 33 (0)1 53 59 61 70
E-mail : rdf@festival-cannes.fr