Cabbage from Swamp Hell

[xaxis]

I'm having a Hell of a time finding any Man Eating Creepers for my skullcap quest. FYI for those that don't know wtf I'm talking about, the Iksar necro class quest for a hat requires Creeper Cabbage to drop from the aforementioned mob in VERY aptly named Swamp of No Hope.

I've spent 6+ hours trudging through the mire of this terrible zone, killing various killer plant mobs and have yet to see a single Creeper. Any tips on spawning these little bastards?