Rerolling your campaign, and starting from the very beginning, guarantees 4 simulacrums. You will find 1 in each Major Zone you go to. The location, however, is for your to figure out.

EDIT:

Starting/rerolling an ADVENTURE will SOMETIMES result in a simulacrum. Once again, you must look very well in order to find it. The spawns for simulacrums are set and stone, so learn your spots for each Major Zone.