So I just successfully swapped out the backup light switch on my '97 Legacy Outback 5 speed. The part I got was from Rock Auto, brand was Airex but it was made in Japan and looks just like the original. Here is a picture of the plug. It is under the air plenum (or whatever that black plastic box that connects to the throttle body is called) on the left side and is the leftmost of the two switches. The one to the right is the neutral switch.
Under the car, at least on a 5 speed manual, the backup light switch is closer to the front of the car than the neutral switch (the super greasy one near the left side of the picture, view is from the driver's side behind the front wheel). The wiring is secured in three clips, two on the transmission and one near the plug.
Thanks to everyone who contributed to this thread, maybe my pics will help somebody else out a bit...
Doug