Ford manuals refer them as air deflectors. You might could make them your self if you can find right material but if you really want to replace them I would go to a Ford dealer to get before they are obsolete. They are there to force air through condenser & radiator but they don't seem to have much affect. I would be more concerned with mud build up in condenser, cooler and radiator than missing air deflectors.
This here^^^My son took us to junk yard this weekend. He found a few parts for his f150.