While not extremely stylish, I live by the Stowaway Day Pack by LL Bean. It has easy-access pockets where I can place a phone, wallet, keys, passport and small items, and inside is roomy enough that I can hold my quart-sized bag, medications, a blanket, electronics, a book and my purse. When I land, I simply repack my purse and the lightweight backpack slips right into my carry-on.