Patoxon via Amazon offers Prime members the Mpow 17-watt Dual USB Car Charger for Apple and Android Devices in Black, model no. MC1-PTX-1, for $11.99. Coupon code "CC78MPOW" drops it to $7.55. With free shipping, that's the lowest total price we could find by $5. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $5.01.) It features dual 2.4-amp and 1-amp USB ports and can charge two devices at once.