I ran across a booth for FlashCards a couple years ago at the Columbus, Ohio, Ford Swap Meet. These guys do a beautiful job, using pictures you provide of your car. They are not inexpensive, but, then again, the really good things seldom are, are they?
Their website is:
FlashCards
I have had signs made for each of my cars. They are a nice size, that will fit in the trunk of your car, and are mounted to a firm board. A display "stand" (a back "leg" for the board to make it stand up) is optional. They are not "wind-proof" or easy to revise, as you had requested, but they are robust, and very impressive looking.
regards,
Jeff