I'll be hiking in Europe in May, and thus carrying all my gear all day, every day. I need to check my internal frame backpack since some of my gear cannot be carried on. What I'd like to do is buy a small backpack that I can use as carry-on luggage and stuff it into the bottom of my pack when I get to Europe - something light and small that I won't mind carrying when hiking and doesn't take up much room.
It needs to hold the things you typically want on a plane, and I'd strongly prefer a side pocket big enough to fit a 1-liter/32-ounce Nalgene water bottle.
Does anybody have any recommendations?