I just bought this Topeak Trunk Bag today http://www.amazon.com/gp/product/B000ZKHN50 and this rack http://www.amazon.com/gp/product/B000FIE3WI.
I stumbled across this trunk bag tonight though (didn't see it earlier): http://www.amazon.com/gp/product/B000ZKATZG
Given that it's only $20 more, it seems like a way better deal. It looks like it has sturdier panels and the pull-out pannier looks really nice. Does anyone have any experience with either of these bags? My main use is commuting, but I'd like to use them for light shopping as well. I'd need to fit a pair of pants, a shirt, (maybe) shoes, and some disc golf discs, and have room left over for other things I might decide to put in there later.