Apparently the new Nexus 7 is very popular, especially the 16GB version. It is already sold out on the Google Play Store and is listed as "Ships Soon." It's possible you might still be able to find one at the various brick and mortar retail stores, like Gamestop, Office Depot, Sam's Club and Staples, but it is reportedly sold out in many of these venues around the country as well.
If you find a store in your area that has them in stock, be sure to post it in this thread, so that any members living in the same region as you might have a chance to grab one.
Source: NexusTablets.net via Google Play Store - Nexus 7 16GB Version