It's a long shot, but try some Ford dealers. If they are willing to do a computer search, possibly they can locate some new fenders in another dealer's inventory.
Secondly, check auto scrap yards.
Third, go to some auto swap meets...it's a long shot, but you can find some bargains if you get lucky.
Fourth, check with some auto restoration shops on the web.
Fifth, advertise in car magazines stating your requirements.
Sixth, pass the word around to your friends and at work.
Good luck! Something will turn up.