I've tried the Spigen case that others are recommending, it's not bad, but it's not super thin, nor is it open around the buttons.

I currently use the KuGi case, and I'm very happy with it. $7 prime, super thin, adds a little grip, but not too much.

Edit: To be clear, the Spigen doesn't cover the buttons, but it does wrap around them more than the KuGi. I found it took a little extra effort to use the buttons with the Spigen, because your finger is hitting the case and the button at the same time. That doesn't happen with the Kugi because it's more open.

For those of you who can't find the Bear Motion case, I'm almost certain it's the same exact case as the KuGi: http://www.amazon.com/quality-ultra-thin-Google-Huawei-smartphone/dp/B014ZJ0538

I've been using this case for several months and it's great, the texture feels nice and it's really thin. Plus it provides full access to the buttons (I hate mushy buttons).