Phottix Battery Grip for Nikon D3100

 Product Description               

 A battery grip for use with Nikon D3100 DSLR.  This grip takes

one or two  EN-EL14 batteries. Effectively double your shooting
time and make a small camera body easier to hold. This grip  comes with

a shutter-release button to make vertical shooting easy and comfortable .
A short cable connects the battery grip to the Nikon D3100's remote
port to provide this functionality.