From my FAQ: You can find these in Grimoire 1F inside blue enemies, and in purple enemies on 2F which you need for the Dark Wing Collection quest. In later quests they are easily found in Ishtar, 2nd Level Terrace N.
If they are not there, I don't know where else.
"As for threetimes, yep, she is a badass mofo faq maker." - ignasia7