Thanks for the suggestions. I ended up finding the rolling 20" travel pack that is the same brand and style as my laptop bag. I think the two will work very well together. It isn't Tumi, but I have been very pleased with the form and function of the laptop bag, and the rolling case seems equally sturdy:

Laptop Bag:
http://www.flickr.com/photos/georgia...n/photostream/

Wheeled Travel Pack:
http://www.flickr.com/photos/georgia...n/photostream/