I'm normally incredibly careful with this sort of stuff, but somehow I misplaced one of the center black plastic pieces that keep the dial wheels on their stand (are they called rivets?) (actually just half of one, the smaller of the two). Where do you think I could get another one?

I would just email asmodee customer service. They’re pretty good about replacing bits.

These are also used in X-Wing for their dials.

Ask an xwung player. Their game was recently rebooted with all new dials. Should be plenty of old ones around.