I bought half a dozen Anker brand lightning cables (
http://www.amazon.ca/Certified-Anker.../dp/B00K4VQZCM) and just left them all over the place. I've got some at the office, each of our vehicles, in my laptop bag, various places in the house. They were cheap, good quality, and now we're never hunting around for a charger or worried about bringing a cable along with us.
On a related note, I also bought an Anker portable battery charger thing (
http://www.amazon.com/gp/product/B00...GEMT2DX5TD9G3J) that was pretty cheap and has saved my bacon on a few occasions.