Lots of manufacturers make fine day packs. Look at ClikElite or Gura Gear or Kata or some of the larger Lowepro daypacks. I went with F-stop primarily because it has a 62 L (liter) bag that can hold a fair amount of camping gear and food for multi-day trips. The medium shallow (non-gripped camera) insert is 11 L, the extra-large pro (gripped pro camera) is 25 L. If you aren't stashing a 15 degree sleeping bag, pad, tent, stove, pot, "10 essentials", clothing layers, it then becomes pretty simple to find bags.