The Buck Naked Drive Variable Voltage Pod Battery packaged as a variable voltage battery.  It is intended for use with nic salt pods and is known for its capacity to accommodate very thick oils.  It works well with pretty much any remotely compatible pods, disposable or not.

In the drive, you will find a 3-inch form factor.  This piece fits snugly into your hand and can be put away quite easily.

All you need to do is fit a compatible pod on the battery and you are in business.  The voltage settings allow you to manage the controls depending on your liquid of choice.