There are hundreds of 30--40 liter day packs on the market. I use an Osprey Talon 33 - because it fits ME!!! Nobody here is going to recommend a specific pack to you because pack fit is critical and almost as individual as a set of contact lenses. I'm sad to say that you will need to take your day gear with you to wherever packs are sold and stuff and try until you find something that fits. By fits, I mean a pack that fits you, your gear and your budget. It's like trying on shoes: fit is everything. Nowadays, packs are sold as fashion accessories as much as for carrying stuff. Don't let fashion override function.

D