The quest item Sida's Bag dropped from the very first black ooze I killed for the Digging Through the Ooze quest. I remember this quest taking forever. Guess I just got lucky. :
Cloned Ooze - NPC - World of Warcraft
A Disgusting Oozeling | WoW Misadventures
Digging Through the Ooze - Quest - Classic World of Warcraft