A fine piece of engineering, if I do say so myself! You will need to travel a bit, I'm afraid, in order to find the incorporeal undead we require.
You see, different climates lend different consistencies to the spectral fabric of the dead. The tortured night elves of Silithus, the spirits of the highborne from Winterspring and the ghosts and banshees of the Eastern Plaguelands should give us the different types of ectoplasm we need. Be sure to place the distiller nearby before you harvest them!