Inca Makes a rack & pinion lift that can be as narrow as 3.75" but I think gets deeper for larger TV.  Their website isn't very good so you'll have to look around for it (photo below).

http://www.inca-tvlifts.com/



I think they also have a more traditional pedestal lift that's around 4.5" deep, but for that you also have to add the thickness of the TV hanging on the front.

I used the one shown above to build into a custom bed footboard last year and it worked out really well.

Here's a photo and phone video:


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