Any smaller electronic stuff charging with a USB... a Jackery Titan battery pack. $30 bucks each on Amazon and will charge a GoPro about 10 times. Charges my iPad Mini four times.
Get a couple and you are set. Awesome for every day life too. Camping, airports, long flights,etc. Compact and light.
They charge devices about the same speed as a wall outlet.
The Jackery battery itself takes a good 12-18 hours to charge from a wall outlet though. Keep it in mind in your planning.
Jackery Titan — Jackery - Empowering life on the go