I've been using the Topeak MTX trunk bag. It has panniers that unzip and drop down on each side, plus you get the storage on top. Works fine for commute to work. It does need the Topeak rack to clip into. No problems at this point. Wife got it for me because she hated the milk crate I had strapped down to my rack. That worked well also, I just tossed my backpack in and I was good to go.