The
Tom Bihn Daylight Briefcase is very lightweight (Cordura exterior weighs 12.5 oz; the ultralightweight halycon fabric is just 9.2 oz.) Solid black-- currently sold out but available soon--should fit any professional environment where you'd be open to a non-leather bag. It's very slick looking in person.
It's not padded, so you need to put your laptop in a light case (I use a neoprene sleeve), but that makes the bag more versatile and cuts weight. I've used it on days even when I don't carry my laptop.
In all, it's a great minimalist briefcase and my shoulder and back are very happy since I started using it.
Tom Bihn does a much larger bag, the
Empire Builder, if you carry a lot of stuff, and I think this one has the open back pocket to slip over a suitcase handle, but I don't have firsthand experience with this one.