1964 and 1965 fenders interchange. Here are locations in USA that show to have left fenders in stock. I can get the list for the right if you need it.
1964 Fender Plymouth Barracuda 2X5 LOW RUST 030206
Call Bud's Salvage USA-OK(Aline) E-mail 1-800-375-2837 1-580-463-2424
1965 Fender Plymouth Valiant 189,65,1BBL 706092
109 U-Pull-It USA-NC(Winston-Salem) 1-336-788-9122 / 1-888-428-2405
1965 Fender Plymouth Valiant 2DR SDN CREAM, 311005
Classic Heaven Used Auto & Parts USA-MA(Brimfield) E-mail 1-888-549-1786
1964 Fender Plymouth Barracuda MAROON,VERY MINOR RUST,C-NOTE P05252
Call All American Classics USA-WA(Vancouver) 1-800-955-4999
1965 Fender Plymouth Barracuda BLUE,ROUGH,WALKUP Q05464
All American Classics USA-WA(Vancouver) 1-800-955-4999