Patrick,
You are correct - but alas, one cannot source the Std/Tourer part separately. Radio Shack does not offer a waterproof version of a 5-pin female DIN and last I looked, neither did Digikey or Mouser. Thus, one is going to have to modify an available I/S sub-harness to get themselves a working connector/lead assembly...unless another source can be found.
Electrical Connection, Vintage Connections and a couple other places sell Hitachi connectors in the pin arrangement that is used by the I/S' lead. What I would do in this situation is to get the I/S part then snip the faulty DIN connector (along with a bit of the cable) off the accessory CB unit's headset lead. Then install a mating 6-pin Hitachi female connector onto the lead and plug in the I/S part.