There are two or three on here, for your consideration: https://omegaforums.net/forums/private-watch-sales/
This forum. Any dealers... consult this forum first. I was gonna reel off a bunch of good ones but they are all subject slip up from time to time.
@Kringkily usually can source anything...and although I don't know if he is a reputable man...he is definitely a reputable seller!
Friend Sidrox, you can't get 'em in a store. You have to prospect a bit.... There is no vintage dealer who specializes in UG, AFAIK. They all get one in stock every now and again, and they run the gamut from dodgy to impeccable.