I have
one of these It would easily hold laptop in the back pocket (a 12" powerbook) and camera body in one side pocket and lens in the other. Inside comfortably fit shoes, a change of clothes, something to read, toiletries etc.
The bag is
TINY and fit under the seat infront. Still can hold a lot.
If I could only fit my 15.4" laptop in that back slip pocket......
/E