Have you tried any local junk yards? I would think that the plastic adjuster nut would not cost more than a couple of dollars, especially if the Sport Trac was wrecked and had the headlight was broken or missing?
Next I would check at local body shops...they have catalogs and part numbers of all those little body parts, clips fasteners, etc. They just might charge you a few dollars more.
Got the adjuster from the dealer. I broke the plastic part of 13032B, but bought 13031C because I only needed the plastic part and it was 13.00 v. $38.00 and swapped the plastic part. About 10 minutes.