I found one at Fred Meyer that works pretty well. I think The packaging said it was designed to hold a Samsung Galaxy or even an iPhone in a case. I saved all the packaging and receipt in case I see one designed for iPhone 6 before October 20.
Have you tried a running belt? I had my daughter use my running belt and it stretched over her 6. My daughters shorts didn't have pockets and I was paranoid about her holding her phone during our hike and the stretchy running belt was great.