Bought a house with no receptacle in the main bathroom. Light switch on wall has only the wiring from the light entering the device box (i.e. the main hot cable from the panel does not come through here). Want to install receptacle next to light switch, wired into the same circuit, without ripping walls apart to get at the light and the main hot cable. Will accept an outlet that is energized only when light switch is on. How is this to be wired?