Its not hard to make a signal tracer from an old AM radio. You need 60 mm of red and black flexible twisted pair, a 0.22 uF, 100V capacitor, a small black alligator clip, a 50 mm length of shrink tubing that will fit over the following probe, and a thin 100 mm long piece of wood for the probe — this can be a skewer stick used for a shishkabob.
The signal tracer uses the audio amplifier of a small radio. I disconnect the detector diode from the hot end of the volume control and connect two wires to the volume control. A black wire from the outer oin of the 3 pin volume control – this is common. The red pin goes to the hot pin of the volume control – the end that makes noise when you touch it. The other end of the red wire goes through a 0.22 uF capacitor, the other end of the capacitor is the probe.