A Tone Generator/Probe can be used to locate a single cable in a bundle of cables. A sound is generated by the tone generator, and with the probe you would touch the cables in the bundle to you can hear the sound generated through the probe.
For cat cable we have PID 8132 that is a tone generator and probe. https://www.monoprice.com/Product?c_id=109&cp_id=10913&cs_id=1091305&p_id=8132&seq=1&format=2