MiniInTheBox offers the Xiaomi Dual USB Port Dual Car Charger for $8.99. Coupon code "322FCDA4C6" cuts that to $5.02. With free shipping, that's the lowest price we could find by $3. It features two 2.4-amp USB charging ports.

Note: Uncheck "Add Shipping Insurance to your order" during checkout to remove the 49-cent fee.