You've probably already tried this, but in an article in Mopar Muscle:
“The original material headliner and Gator Grain vinyl for the vinyl top came from Legendary Auto Interiors.” Legendary Auto Interiors, Ltd., Dept. MPRM, 121 West Shore Blvd., Newark, NY 14513; (315) 331-0903; (800) 363-8804, fax: (800) 732-8874.