Hello - I am looking to buy an extra charger for my 2018 13" MBP w/TB. In particular I am looking for a charger that I can put in my school backpack and travel with in situation that I might need to charge. I do not need it to be a fast charger but would prefer something that is small and lightweight. Is it possible to use an iPhone charger with a USB to USB C cable? Any other small travel chargers people recommend? Thank you!