I have a Lowepro CompuTrekker Plus AW Backpackand would like to buy a Lowepro accessory bag to store my 580EX flash and also to attach to my backpack. Is there such a bag? I cannot find one. The closest thing I could find to match this description is the Lowepro Lens Case 2 but it seems like it would be a little bulky for what intend to store in it.