Hmm, this forum doesn't store photos, have to be at a public URL.
This advrider thread includes photos of a 92 R100R Dash:
Using the switch socket might work. Powerlet lists drilling an 11/16 hole for the socket, and the switch blank is just 1/64 over 11/16 wide. Might get a little more wiggle room, or have the switch hole to powerlet socket rise a little above the dash and get wider to provide a little more material to the adapter.