I use the Tumi linked below which has a pocket for a laptop and also a tablet. It easily caries my 2010 13” MBP and IPP. Before I started using OneNote I would put my notebook in the centre section.
I like it because it has the normal Tumi organisation but as I travel weekly for work with only carry on luggage it is small enough to sit on top of my case and ride along easy. As it is smaller than your average laptop case I can also make it work for casual use when needed.
The expandable zip makes it easy to carry extra on the few times I need it but it is not used often.
https://uk.tumi.com/p/small-screen-expandable-laptop-brief-026120D2