I ordered a Timbuk2 Classic Messenger bag in back in October and it's been holding up pretty well. They're able to be color/fabric customized and are made in the USA - at least the customized ones are. MSRP is $150, but they run sales from time to time. I think I paid $140 shipped. I carry a 14" Thinkpad and got a Medium sized bag for a little extra space. Included in that $140 was a grab handle, matching shoulder strap pad, and their "crater" (read: padded) laptop sleeve so it was a pretty nice discount.
Personally I like that Timbuk2 does not look like a cool-guy bag. When I was shopping I also looked at the ITS messenger bag as well as 5.11's offerings but they would stick out in my environment and to be honest I thought they were too expensive for what they are. For your needs, you could probably get away with a size small, but I like that I can stuff a jacket or other items into mine and it's not bursting. From time to time I'll use it as a weekend bag with toiletries and a change of clothing.
link to their site: https://www (DOT) timbuk2.com/pages/customizer#/product/18-custom-classic-messenger-bag/size/4/customize
Some photos of mine. The exterior panels are "nautical" and "surplus" and the liner is "gunmetal". NOTE: The blue isn't as bright as the pictures make it seem. It's also waterproof.
This is with my 14" laptop and a small Magpul Daka pouch. The expansion and compression of the bag based on what you're carrying (or not carrying) is pretty impressive.
Regardless, if you don't get it on sale, a custom bag that's made in the USA for $150 is hard to beat - even if you're like me and don't ride a bike