They do make some pretty decent 12 volt TVs, this would be the most efficient option, otherwise a small inverter will work like previously mentioned. They cost a bit more but a pure sine wave inverter is the better investment.
The radio alone is a very good suggestion, but if that's a no-go then see if there's an option in settings to dim the screen as this uses the most power. You also should consider setting the timer to turn the set off in a few hours.
Remember, lead-acid batteries don't play nice after discharging below 50% too many times!