In no particular order: Tourneau (disclosure: I used run the vintage division, but no personal connection there in 10 yrs, however; high-priced, but good quality and they will stand behind the product); Aaron Faber Gallery (owner, Ed Faber wrote a book on American wristwatches, very knowledgeable; his stuff, like Tourneau's will be serviced and warranteed); J&P Timepieces (Jeff & Peter). Google them for addresses. You can mention my name and get exactly the same price they charge everyone else.
All these folks have been in business many years and are reputable. There are also a whole slew of dealers on 47th St.; be more careful there.