I have two ATD UVMCs. Bought both from our friend, Mr. Harris. You can see them here
Before I bought the first one, I had seen exactly one in person, at Guitar Center in LA. It was a used Japanese swirl, beaten to hell. I've seen one other in a store since, at 30th Street Guitars in Manhattan, also a Japanese swirl.
I have no idea how the myth got started, but there are many people around here who believe that there are only 60 or so Japanese swirls out there. From what I've seen on eBay, elsewhere on the web, the two in stores, and just trolling around here over the years, I have a pretty strong feeling there are far more Japanese swirls than ATDs. This has been debated to death on this forum before, so I won't say anything more about it here. You can do a quick search to find out more.
Japanese swirls seem far easier to come by than ATDs. UVMCs in general are fairly easy to come by, but the market seems to go through cycles. Sometimes you see a bunch at once (I remember once there were three or four on eBay at once) and sometimes there won't be any for a month or two.