Audio switch like in aircraft chair arm

[tmd1]

Hi Guys,
I have been asked to replace a mechanical rotary selector switch with a push button solution. There are eight mono audio channels to switch to a pair of headphones.
I had imagined that there is some sort of chip or simple circuit that will let me toggle up and down with a display that shows the channel (although maybe not necessary and might add extra expense). There are ninety of these in the auditorium so it is worth doing it right.
The other complication is that it seems the audio is distributed on a 100V line. There is a transformer in each switch box at present.
Where would I start to look for this sort of thing? I have tried searches in Radionics and Farnell as well as Google of course.
Another way to do this possibly would be a totally mechanical solution with up down buttons but the customer seems to like the idea of the aircraft arm rest.
Thanks in advance for any help or advice.
Neil.