I just got a T3 a few weeks ago, and bought the Canon backpack -
http://accessories.us.dell.com/sna/...=1838860&acd=spla_pl_dhsea:028083,,901pdb6671
With 3 lenses and all the various equipment, the bag is nice, but I still have alot of room in it, especially the outer pockets, which I stuff with dry food and other camping things. I then attach the backpack to my camping backpack, or stuff it in a waterproof bag and put it in my larger backpack (old style Army duffle-backpack modified).
As a bag itself, it might be too big for what you want... I find myself taking it with me, then carrying a spare lens in a cargo pocket, and leaving the backpack in the car when I go out to the metroparks. Been interested in a smaller pack for those outings.