The black leather Moto 360 is currently up on the U.S. Play Store, though it probably won't last long. After going out of stock pretty much immediately at launch several days ago, it is already listed as shipping September 22nd, a full two weeks from now. The gray leather variant remains out of stock.
Update #1 9/8/14 1:55pm PT: Aaaand it's gone.
Update #2 9/9/14 1:15pm PT: Back in stock.