Hands down, the best and easiest place to get this drop if you have a higher level Wizard is from the Death Ghultures in Mirage. This is one of the very first quests you get when you open Mirage. If you head towards Caterwaul Canyons, starting from the World Door, they are the first mob you see. They are a pretty easy kill at the required level to reach them with only 2,450 health. The drop rate is far more generous than it is in Grizzleheim or Wizard City. As a bonus, Evil Magma Pea drops here too.