Nikon MB-D15H for Nikon D7100 (with Remote) Battery Grip by Wasabi Pow – Wasabi Power
Vello BG-N11 Battery Grip for Nikon D7100 & D7200 BG-N11 B&H
TUTORIAL | Nikon D7100 Battery Grip - How to Use a Battery Grip - YouTube
Amazon.com : Neewer® Vertical Battery Grip for MB-D15 Works with EN-EL15 Battery or 6 Pieces AA Batteries for Nikon D7100 D7200 Digital SLR Camera : Electronics