I would think rubber would be king for that job and alternatives have been found in the aftermarket world. Look at @NCFJ 's build threads for the tech tip. That grommet gets rotated and squished, lots of dynamic forces on it.
I got a small trim piece from @ChaserFJ60 , great piece and excited to put it in. I first sanded with 600 grit sandpaper. I should have done it longer, but its smooth enough. Next I hit it with plastic adhesion promotor so the paint actually sticks. Then hit it with SEM 17073 which was way too...