Kanger MT3 Replaceable Clearomizer with viewing window (Bottom Coil) - $5.99
The link above is to Carolina Vapes, and they only carry the chrome and the black versions so far.
The Kanger MT3 is the same thing as the Kanger T3 but with a slotted metal sheath around the tank. The T3 was the winner of Phil Busardo's recent Clearomizer Shootout.