When you unpack your suitcase and find you're missing a charger—before you hop to the nearest electronics store or rig an emergency solar charger—head down to the hotel front desk.
Cell phone chargers are the number one most left behind item at hotels and chances are they'll have a box full of every type imaginable. (This will probably also work with rental cars!)
Most will have been abandoned there for months, and chances are you've forgotten yours behind at a hotel before. Think of this as a giant give-a-penny-take-a-penny bin for frequent travelers.