Amazon.com : Kastar 2-Pack EN-EL4a Battery 11.1V 3200mAh Replacement for Nikon Camera D2Xs, Nikon Camera D3, D3S, D3X Camera, Nikon Camera F6, Nikon Grip MB-D10 D300 D300S D700 MB-40 (W/BL-3 Chamber) :
Amazon.com: Synergy Digital Camera Battery, Compatible with Nikon D3X Digital Camera, (li-ion, 11.1V, 1800 mAh) Ultra High Capacity, Replacement for Nikon EN-EL4 Battery : Electronics