Today, I learned that the slide-on plastic tow mirrors for the 2002 Expedition fit my 2007 XLT Expedition pretty well. I can't remember the brand, but I got them at an RV dealer.
I think they will stay on OK, not vibrate, but I did two easy mods on each, a 1.5" dia hole in the bottom for the mirror lite to shine thru the underside and cut a little of the inboard at the bottom, so the mirrors can be folded against the vehicle. I got them for $39 each. They come in LH and RH models.