Or on any car?
Lincoln did offer this option on Town Cars back in 1988 so there are some available.So is it possible to build/install one on a car that does not have one?If so how much would it cost?

l think it might be possible l have seen a new Chrysler 300C and the owner turned it into a convertible

YES, it is possible. Ive seen it done many times. the more popular way l have seen it dont is the sunroof more toward the back of the car above the rear seats. It could be around $500 up to $3000 depending on where you go or who you know.

Yes, there are shops that do them, however, l have read statistics that up to 50% of them leak, so do not be surprised.

Sure it can be done. On the few Lincoln Town Cars I've seen with sun roofs ( l own one, a 92) they are most commonly found in Cartier edition units. Several after market suppliers can get the parts/system and it can be built into the roof by fabricating the roof to fit the measurements.

yes, look at aftermarket installers. It may be cheaper to buy another car that has one.