it's in the bag, but which one?

In about 10 days I will start schlepping a kid on the bus with me in the morning. It will be Oliver for a week, then Eleanor for the foreseeable future. (Long, complicated logistical story. Very, very boring.) It's not a long ride, and I'll get a seat most days, but it's still the bus, with a kid, so I'm looking for ways to make it all go as smoothly as possible.

Step one is finding a really good bag. I'm a bit of a bag junkie and find searching for a great bag to be fun, but in this case I am looking to you, oh wise internets, for suggestions. I have looked a little and nothing is speaking to me yet.

Here are the key things I will likely be carrying most days: 

• kid (almost 16 months old and about 28 pounds)
  
• lunch (mine)
  
• mom crap (I don't have a huge purse but I carry more than a wallet)
  
• kid crap (not consistent, anything too big I can send in the car with CD for arrival later)
  
• work crap (the occasional file folder, nothing more)

Sometimes I may have a laptop but I am working hard to make that a rare event.

Ideally, the bag would be lightweight and fairly professional looking A diaper bag with cute little elephants and flowers isn't gonna cut it. Neither is a 10 pound leather number. Since I work in an academic environment I don't have to go with a corporate look.

Leave your suggestions in the comments!