You're talking about the flaps that are molded into the trim, right, I think there's one about eye level and then another above your head?
Bonding metal to plastic can be hairy. Were it me, I'd get some thin styrene sheet from the hobby store; they sell it for models, Evergreen being a popular brand name. Worst case you can get it from https://evergreenscalemodels.com/
You might have to double it up to fit into the slot in the roofline, as they come in like .010", .020", pretty thin. Anyway, bend that into the L shape to fit into the roof, then glue to the pillar. I think epoxy or a plastic welder. I'm partial to this stuffhttps://www.tapplastics.com/weld_on_16_cement
(that's my local dealer, I imagine if you have a local plastic place they'd have it or something akin to it.) I find it melts into most plastic and bonds them pretty well.