This universal AC to DC power adapter for laptops and tablets is much better than an inverter in your Vanagon. It has a variety of power plugs available that will work with almost any brand of device, and use is extremely simple requiring only a few moments to check the power needs of the device.
You can read the power requirements off your normal power supply for the device, usually on the back under the "OUTPUT" description. It will read a voltage which you then select on the back of this adapter. The adapter also has a separate USB plug with 5V DC output for charging devices which use a USB cable to do so, such as cell phones and many tablets.