I just completed this repair. The Expedition I bought had this broken, so I went ahead and ordered the part to replace it. For some odd reason, parts.ford.com labels this as "Dashboard Air Vent Lovre", but it is the ceiling one. This is the part:
https://parts.ford.com/shop/en/us/dashboard-air-vent-louvre-p-jl1z19893bq?pdp=y. It currently sells for $28.70.
To add to the post by
@yeahyeahbut, it is indeed easier to approach this from the door side of the louvre. I used a trim tool to yank the existing one out. Just make sure you're putting the trim tool between the metal frame pictured in yeahyeahbut's image and the louvre frame so that you don't end up with the metal frame out if the ceiling. A little force is required for all of this, but nothing excessive.
I will also say that once I pulled out the "broken" louvre, I inspected it and realized that it wasn't broken at all and it could be fixed by putting things back where they should be. In fact, the construction of this louvre seems to be pretty sturdy. I would recommend making sure yours is broken before pulling the trigger on a replacement. Now I have a spare
