I use this bicycle phone magnetic mount attached to my mic stand, but it'll fit wider diameter tubes too. Since I already had a magnetic car phone mount like this, I already had the stick-on pad to mount the phone. No clamps or anything to mess with, just put the phone on it and it's not moving.
I recently purchased a mount for my iPad. I wanted something that I could easily attach to any type of stand or even a bass drum hoop. I also wanted something that was fairly durable, so went with Tackform. Check them out HERE