Power banks. I'm a huge proponent of them because it solves this problem while also not keeping you stuck at an outlet somewhere.

You can charge the portable power bank at any USB port: computer, wall USB, airport, clock radio, airplane, vehicle, public kiosk, etc. Then it'll keep a charge for weeks and allow you to charge your devices anywhere. And because it doesn't have storage capability at all, you'll never be susceptible to this kind of attack...