CyberPower CPS150CHU 150W Mobile Power Inverter with USB Charger for $17.99 shipped.  It is sold by 1saleaday through ebay.  Here is a screenshot for your reference.  It features built-in surge protection, USB charging port, automatic-shutdown, 2-in-1 connector, built-in splitter, self-retracting 36" tangle free cord and more.  Most places have it for about $37.