Check out the VOOPOO PnP Pod Tank, featuring a 4.5mL bottom filled capacity, PnP Coil Compatibility, and is fastened by a 510 connection. 

VOOPOO PnP Pod Tank Features:
26mm Diameter
4.5mL Refillable Pod Capacity
Bottom Fill System
VOOPOO PnP Coil Series
0.3ohm PnP-VM1 Coil – rated for 32-40W
0.2ohm PnP-VM5 Coil – rated for 40-60W
Bottom Press Fit Coil Installation
Dual Slotted Bottom Airflow Control Ring
Threaded 510 Connection