Only a so-so solution, but I haven't found anything much better
I got this to hold my cellphone ad a few other items while rolling around. It has a tendency to drift along the frame tube, so I interlaced the uppermost straps with those from my seat cushion. It's too small to hold my wallet and cellphone together, but big enough that the phone falls sideways to the bottom and can be difficult to retrieve in a hurry (and I'm rather dexterous).<br /><br />So, especially considering it's not expensive, I guess it's the best solution for now.
Rating: 3 stars