Yes, the generally accepted method to power a 12v DTV is via a 12v plug AKA a cigarette lighter. Not all DTVs are dual power, some are actually 12v only so you may want to make sure you get a dual power DTV if that is what you want. On some units you may have to purchase the 12v plug as an accessory, if so make sure you follow the manufactures recommendations.
So it seems as if step one is to install a 12v power plug in the POD. It may be a good time to add the popular triple function set that so many others use with USB charge ports and a digital 12v meter to help monitor your 12v power supply.
Another option is to install the plug and then use a small power inverter to power the DTV you have now, not necessarily a better option because you need a 12v plug for the inverter anyway and also have to layout the cash for the inverter as well.