Most likely your "trusty" Skymaster has a built in avionics power switch
Part #S2281-1 - Avionics Power Switch @ $434.78 each from Cessna Direct
http://www.cessnadirect.com/search.p...=search&page=1
You could check with Commodore Aerospace, although he stocks mostly earlier model parts, as they are new military surplus. Don can be reached at -
nieser.02.337parts@juno.com
Also check these sources
http://www.controller.com/list/parts...1-1&pst=starts