In the spring someone on here menioned the bagalleni bag. I know several of us ordered one. You can get one from their website, but a seller on e-bay had them as a buy now item, at a much cheaper price. Depending on how you adjust the strap it can be used as a messenger bag or a one strap backpack. It has LOTS of pockets, but is quite a bit smaller than a regular backpack and is lightweight. It worked well for me in May. In fact I had a couple of smaller pockets left over that I didn't even use.
I had an autograph t-shirt and pens, camera, cell phone, mister fan, id, AP, room key, safe key, credit card, a small coin purse, my itinerary, a small note pad and pen, poncho, lip balm, powder, bandaids, mole skin, small sunscreen and a small guide book and still had room left over. Again it is smaller than a traditional backpack, but holds alot because of the pockets. It even had a pocket for my Brita bottle on the side.