Hey, lost your adress but here's some info:
I checked my Bentley book wiring diagram for the 1971 Super Beetle and
it seems that the rear defogger switch is a rocker-type switch located
to the left of the steering column.  If it's not there, check under the
dashboard, it may be an aftermarket job and they put switches in weird
places.  Other than that, I don't know where it would be.  HOpe that
helps.

Sean