An excellent zippered bag for storing small items.
Top pocket, protects your phone and keys in your backpack. After one needs another.
It can already hold more stuff than a small one. For example, for driving all the chargers needed on the trip. For example, it can hold a camera battery charger, a pair of small phone chargers, and a laptop charger. A fair amount of your alternative even first aid supplies or papers needed for the trip to protect against moisture.