How many switches do you have or plan to have?
What kind of Accessory power is available for the relay circuit?
Is it acceptable to use a $2 DC-output wall-wart (which requires access to a wall-outlet socket)? Or is it desirable/required to only have power from the Accessory AC (e.g., 14V, 16V) from an existing transformer?
Are you willing/able to solder a few components?
You should be able to do this for ~$5 per switch using a ~$3 timer-relay module from eBay/Asia and few 10-cent components. Answer the above questions and I'll cook up something.
