No source for that switch - one of those parts in the stash that I've had since the last century. I'd think it would be easy to find but then again, Nothing is so easy as the job you imagine someone else doing.
Regarding the power LED: the LM340 standby (quiescent) current is about 3 mA typical...so a 9V battery would only last a few days if left "on" inadvertently. While a power LED would also draw a few mA, presumably it might catch one's attention at the end of the day reminding to turn it off and save the battery. A tradeoff for sure. Of course if track-powered using your optional power method, the LED power is not an issue. Matters of this significance are above my pay grade. 
