To be tied to a composite input somewhat defeats the object of a portable TV!
Post an out-of-focus photo of the screen in the Displays section, under a heading of 'Help me...'?
I have an old Casio pocket LCD (2.5"?) with composite input. I used to use it as a first-level monitor for commissioning video surveillance gear.Unless the interior is very highly integrated, there's probably a point after the RF section where you could tap in composite.