I use a Jandd Mini Mountain Wedge on both my MTB and road bike. It'll fit what you need, but it's probably a bit small to fit your cell phone with the rest of your stuff. It uses a buckle instead of velcro on the straps so you can compress it if it's not full. Performance has it on sale for about 10 bucks. I've been using the one for my MTB for about 3 years.
Dean