What time is it? http://www.dcuo-db.com/style/shaman Click and it should show you the name of the mob drop and location at the bottom.
The Hospital Earth Duo end boss drops it like 25% of the time (took me four tries to get it, took my friend 3). Well... someone above actually answered you with a smart question on what powerset. The one from the Earth duo is a troller headpiece. Good luck.
I think it's the hospital... it's not the one where you have to stop 100 guys from entering the duo.. not that one. And it's not the end boss that's like a mini-meta and changes into 3 forms. It's the one where the boss is activated on a yellow triangle and there are 4 turrets surrounding him. I think that's hospital?