I like my LL Bean Continental Rucksack. I use it daily to carry my laptop, NC headphones (in case), Kindle, umbrella and a small zip organizer of cords and electronic gear. Still plenty of room for a couple of packing cubes with clothes for a long weekend. I believe it's 33L in volume and has a sternum strap and a padded stowable hip belt.
https://www.llbean.com/llb/shop/7924...=http%3ALogoff