The button went back on easily with the two-tubes stuff from Pep Boys. On the subject of rearview mirrors, have done some research on compatible aftermarket/upgrade options, and of course, none of them use the 968 mounting method. So, no apparently any upgrade would require replacing the glued-on button, using some sort of adapter, etc.
The other thing I've found is that most aftermarket mirrors are 10.25" wide, whereas our OEM mirror is about an inch narrower. Does that make a difference? Seems it might interfere with the sunvisors in some situations. And a slight reduction in forward visibility.
Has anyone seen how they mount the rearview on newer models? There was an EBay auction recently for a 996 mirror with autodimming. If it shared the round button mounting, this might be an option. It's likely also smaller than the 10.25 aftermarket units.