Amazon.com : Neewer Professional Vertical Battery Grip Replacement for Nikon D3100/D3200/D3300/D5300 SLR Digital Camera, Works with 1 or 2 Pieces EN-EL14 Batteries : Electronics
Nikon D3100 With Battery Grip by TheXtremesoundz on DeviantArt
NEEWER Vertical Battery Grip for NIKON Work with EN-EL14 - NEEWER – neewer.com
Phottix Battery grip for the Nikon D3100 or D3200 - YouTube