Source MeiKe MK D3100 Vertical Battery Grip pack for Nikon D3100 D3200 EN-EL14 on m.alibaba.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
Nikon MB-D17 battery grip for D500 now on sale at Amazon US - Nikon Rumors