I bought the zacuto one. It's $35, kind of overkill, but I had enough of $7 cables.
http://www.bhphotovideo.com/c/product/827083-REG/Zacuto_Z_BHDMI_36_Standard_To_Standard.html
If you have the chance can you snap and post a quick picture of this cable on your rig? I am particularly interested in the area where it attaches to the camera and how the angled cable fits and routes up to the Ninja. I too have had issues that are apparently cable related. Thanks.