Hi Mike,
I'm not quite sure exactly what you require but presume it's something similar to piano pedals. There used to be some 2 pedal units of Italian origin around but I don't know about 3 pedal units. These could then be interfaced to the 4 input controller available from Carillon -
http://www.carillonstudios.ndirect.co.uk/ Alternatively there was circuit information at
http://home.no/gjg/bobs/Hruby.htm which could be adapted to make your own if you have the necessary skills.
Hope this is of some help.
Cheers
Len C.