I installed a helicoil into the plastic knob on one shfiter button but it ripped out the helicoil , you can try to helicoil the button , I would use some JB weld behind the helicoil if you try that . Steve is correct it is keyed to the outer knob & they both thread down together but do not thread it on too far or the button will not depress far enough to clear the detents
Steves [Quapman] shifter is by far the best option , it is all steel & you will not have any issues with it & it installs in seconds , I have put those shifters in a few cars now & my customers love them