Ectoplasmic Resonator

Source
This item drops from the following in Western Plaguelands (or Eye of Naxxramas in Stratholme), provided you have the Vitreous Focuser in your bags:


 * Hungering Wraith
 * Dreadwhisper
 * Araj the Summoner
 * Cauldron Lord Soulwrath
 * Haunting Vision
 * Wailing Death


 * Spectral Attendant

As a quest objective

 * Gahrron's Withering Cauldron