http://www.arkon.com/bike%20mounts/bike-motorcycle-mount.html
I've used an Arkon mount in the past, though I had to use a little tape to make the removable portion of the mount a little tighter so it wouldn't slide out. I also put a couple wraps of electrical tape underneath the clamp of the Arkon mount so that it wouldn't rotate around the handlebars.
Alternatively, I had an extra belt clip for my Otterbox (for iPhone 5) that my wife wasn't using, so I drilled a hole through that and used a bicycle accessory clamp. Now I can leave my phone in the Otterbox, and just clip it into that mount, rather than having to remove the Otterbox to allow the phone to fit into a phone-specific mount from another manufacturer.