Door panel belt or window seal molding glue?

I have thought about Epoxy as well as the rivets.

The epoxy would need to have like a self mix tip and I do not have that setup.

The rivets would require a backup.

I did not think about double sided tape.

The 3M double sided tape is tough stuff, and I think would work well for that.
I use it for emblems and other things that have to stay on flat surfaces without pins or studs.
Actually never had anything come loose.
The gorilla products are pretty damn good also.

If you use 3m weather strip adhesive, use black. :D