You do not mention a model year. On a 98 and I believe 99 and 2000
the VR is inside the alternator, likely the same in even newer models. This
is under the power steering pump on mine. I am considering to have my old
alternater looked at and get an estimate to rebuild by a local company.
You would have to open the alternator to some degree to replace the
regulator. A task that is I believe is rather difficult with the
alternator in the viechle.