seeking a recomendation

I'm not sure where to post this so I'm hoping onebag can help. I'm a band director and I carry large music scores (up to 12 x 18) and I'm looking for a bag that I can use to transport them back and forth from work. Ideally it would be less than $200 Canadian. Closest thing I've seen was the timbuk2 alcatraz backback but you can't get that in Canada...

Thanks!