Bike power bank holder

I wanted to use my iPhone mounted on my bike to track my movements. But also I needed a externel power source to keep the iPhone running the whole trip. So I bought this: http://www.amazon.de/gp/product/B009ZP12UI/ref=as_li_ss_tl?ie=UTF8&camp=1638&creative=19454&creativeASIN=B009ZP12UI&linkCode=as2&tag=socug-21

And to mount it on my bike, I printed this "power bank case".