Most of the units with the in line transformer, are the ones with smaller screen sizee.
While visiting places that sell LED and LCD televisions, check for units that have a transformer built in to the power cord. Check that transformer for output voltage. There are many (not all) of them that output 12 volt power to the television. I have two Insignia's that do. After buying the television, I went to Radio Shack and bought a 12 volt plug to fit the TV. I can use them on 120 volt, when plugged into shore power, or on 12 volt when boondocking. No need for an inverter.
Curtis makes a 24" LED with DVD, that has the 12 volt transformer.