I'll look into the 3M spray adhesive! Is this
it?? The description says it is used to attach upholstery cloth to paint or bare metal. However, the part of the door that the car trim is attached to isn't metal: it's more like a thick plastic.
That looks like the stuff but they have changed the can since I used it. I actually used it to attach headliner fabric to metal, so I don't know about fabric to plastic. It certainly seems
sticky enough to hold whatever you'd want, but I guess you'd better check the label.
We had an '02 Elantra. They are good cars and you probably have many more good miles ahead of you, but a lot of trim and minor things seem to just "let go" around ten years.