Yugster offers the CyberPower 150-watt Mobile Power Inverter with USB Charging Port, model no. CPS150CHURC1, for $9.97. Coupon code "FREEYUGBUCK" drops it to $8.97. With $3 for shipping, that's the lowest total price we could find by $20, although we saw it for a buck less two weeks ago. This device converts 12v DC power into AC power and features an AC outlet, USB port, and pass-through DC outlet.
Note: The countdown timer on the product page does not reflect an actual expiration time and resets daily.