put a new headliner in and broke the push tab...
I call them plastic body panel push pins, and you may be able to find one at a Pep Boys, or even an Autozone, where they keep all the nuts, bolts, and miscellaneous plastic push pins, or possibly in a HELP! section (although I doubt it). You may be able to find one at a junkyard. You can use a cheap plastic interior trim panel removal tool set to safely remove these types of pins without damaging them (also found at auto parts stores like Pep Boys, Autozone, etc.).


