I found some rubber "grippers" in my local Walgreens that work perfectly. They are made for the bottoms of ladies shoes, some sort of black crinkly rubber, roughly egg-shaped, a few thousandths of an inch thick and they are self-adhering (peel off a paper backing). They're about 2" by 3" and are 2 pair for $2.99. They stick nicely to the back of the Fire and make it extremely easy to keep a good grip