If you're willing to do your own wiring you could look into boost/buck converters. I bet just about every TV runs on DC anyway so you'd just be converting DC to AC with the inverter then back to DC with the wall plug on the TV. If you can figure out the voltage it needs you should just be able to set the converter to the right level. Also would depend if the power supply is built into the TV or on the power cord, I assume you'd want to bypass the power supply somehow but I don't know what happens if you feed a DC current to a standard AC power supply.

If I was you I'd test this on a cheap TV you don't mind damaging though...

This guy built one with a battery bank for his laptop: https://www.youtube.com/watch?v=ZQjazsiyr8s

This is a test of a particular converter that I've been thinking about using to power my laptop. https://www.youtube.com/watch?v=AGGkljZIk8k

I've been planning to do this to power a laptop but haven't tried it yet.

There's also this: https://www.amazon.com/Volt-Power-Cigarette-Lighter-Socket/dp/B073Z6PTX2

I don't think TVs pull much current so I'm thinking you could do some research on a store bought universal DC power cable for whatever TV you want.