I've recently started biking to work and have been experimenting with ways to carry my stuff. At this point everything I need fits in a small trunk bag that sits on my rear rack - except for my work laptop (15" Macbook Pro). What's the best way to carry this one last piece? Do slimline, laptop-and-not-much-else panniers exist? How about lightweight, small (but not too small for my laptop), NON-SWEATY backpacks/messenger bags?
Please assume that, for now, I do need to carry my laptop back and forth (can't leave at the office). I would also prefer to keep my trunk bag setup as it allows me to easily go on non-commute rides without having to transfer stuff to another bag.