Were you thinking of something like this?

Here is a link that might be useful: accessory bags

Thanks, noinwi. That looks like what I had in mind.

Here is a real nice one from Simplicity. Haven't tried making it yet so don't know if it is easy or difficult.

http://www.simplicity.com/dv1_v4.cfm?design=4391

Thanks Diver mom- That is the pattern I ended up using. Its a great one. I posted a photo (although it is blurred) on the gallery. I modified the strap since my daughter wanted one of the fabric and I added an inside button closure to secure the laptop and made it just slightly smaller. It has an inside large zip pocket and a patch pocket. I would recommend this one.