There is a distinct lack of suitable 18th Century traveling coaches in the 28mm market. Many of us have to resort to the out of date 17th Century (ECW) coach made by Redoubt. I have seen some other "fantasy coaches " here and there, but none are truly suitable for our period.
I did stumble upon a likely candidate in the American coach reposited in the Beekman Collection. This is the real thing, not a scale model.