You might try eBay. I got a nice used power/heated mirror for my Silverado there when the car wash broke mine. I'm not sure about the Fords but with the Chevys it's cheaper to get an entire mirror assembly used than to get a new piece of glass.
my old man backed into the garage and hit the wall and broke his mirror off, got the complete mirror with signal and heat for just over 100 bucks from the dealer.
my old man backed into the garage and hit the wall and broke his mirror off, got the complete mirror with signal and heat for just over 100 bucks from the dealer.