Can anyone recommend a back pack? I'm headed to Las Vegas soon and I think a backpack would work much better as a carry on bag and carrying it around the Grand Canyon. So, I need it to hold 2 bodies, 3 lenses, a flash, a tripod, and possibly my laptop. I'm really short (5') and it has to be small enough to work as my carry on bag. Am I asking too much for one bag? Thanks for any advice/help!