Alas radio shack is no more but you can still find electroinc parts if you shop around.
The circuit I built was built into a 12 volt Plug.
Tip went to a resistorm as I recall about 450 Ohms. and the other lead of the resistor to the tri-color LED. if you can not find a 2 lead Tri-Color get a red one and a green one... Connect the resistor to the short lead on one and the long lead on the other (or however the two leads are identified) DO NOT SOLDER (yet)
Connect the other lead to the "Ground" contact and again do not (yet) solder
Plug it in in to a known good outlet GREEN only.. Solder and finalize
RED. Swap the leads around and try again
now plug into the suspect outlet.. RED bad Green good.
