I was dead set against making one, but in the end I used a rubber shaft clamp like the one below, then hold the phone against the flat part of the clamp with elastic bands.
The big plus for a lazy so and so like me is that I don't have to switch my phone between cases to use it.
Hang on with th ag visit Darren. I've got one you can have for nothing if you want it. It was bought as a present, I've never used it!! Pm me your address