Nope - I was confused.  I thought you meant plug like cover for unused hole
in dash.  You meant plug like female power outlet.  Location -- just east of
steering wheel -- is where the green timer knob sits for the gas heater if
any, as on my 81 aircooled NON-Westy.  What you're describing sounds like 
something else again.  Does anyone collect VW product brochures?  It would
probably get a mention in the features list.
B.