We have been using (for 2.5 years) the backpack that our medical center grab-bag of free baby goodies came in, so it is green with "mid north health" printed on the back not "Gucci". It is brilliant - backpacks keep your hands free. The pocket we use the most is the drinks one on the side, which is starting to tear. The new grab bag I've got from them is an even better quality navy backpack, which is currently packed with all my hospital stuff

Honestly I reckon you could just go a plain schoolbag rather than anything specifically baby.