I'm amused at the selling approach. Calling a car without aircon rare. I had a dealer telling me that red was the rarest colour to justify a silly price and factually, maybe that's true but you could say that it's the least desirable colour as well.
It feels like you're saying that 3 previous owners is a negative thing? It's quite easy to get to that on limited supply cars, you can't infer what you would on a normal production model with multiple owners. It's usually in the hands of the third owner by the time the car even gets run in. A friend of mine has a 6 owner CSS with 1400 miles on it.
You have to buy these cars on condition otherwise you'll be on a perpetual search and as time goes on, those low/no mileage cars will push into ridiculous collector premiums.
Good luck with the search and pictures when they arrive please.