Concur. The best thing I've found is to hunt the Shadow Wyrm in Destard Lvl 2 with your best armor until you've killed 10 or so. Then, switch to high luck armor and EV the Evil Mage/Demons nearby until you get a drop. I generally can pull one every day this way.

I tried Fel, but M0O and COP kept killing me, even on the second or third levels of the dungeon.

If anyone else gets a better drop rate, please post your method(s).