I got them in Dragon's Valley, Cemetery, Altar, Kartia, Blazing Swamp, just not in high numbers.
They are also given as quest reward. I forget the names of the quests, but you get 10 of them at a time.
Last place to get them, also rare, Is when you see those special Dimensional Chests pop up on the hunting grounds. Click on it and it takes you to a brief instance where you talk with a demon, play a game of chests, and blow up barrels to get various buffs. I saw one of those just the other day in Altar.