It's not a grip, it's an adhesive backed "phone grip." Here's a link. I put 2 on mine but you could very easily just use 1. Search my post history and I have pictures with them attached.

LoveHandle Universal Phone Grip for Most Smartphones, Mini Tablets and Cases, Black Elastic Strap with Black Base, LH-01Black https://www.amazon.com/dp/B01CIN6AXM/ref=cm_sw_r_apan_i_XP5ASTBB203WZPCQAAB4?_encoding=UTF8&psc=1