The new Nexus 7 is just now filtering out to expectant owners, and Google itself hasn't even shipped the product. That hasn't stopped Poetic from tweaking its popular Slimline case to fit the new Nexus. The case won't ship until August 23rd, but it's going to launch for only $5.99.
The Slimline is a flip case with a folding cover that can prop up the tablet in landscape orientation. The versions for the 2012 N7 and Nexus 10 have gotten good reviews, especially considering the low price. It's a nice-looking case too. Note, the images appear to feature the 1st gen Nexus 7, but this is probably a close approximation of how the new case will look.
The only color currently listed for the new N7 is black, but the others are sure to show up at some point if you want to wait it out.
Update: there's also a Slimbook case for only $3.95. More colors for the Slimline are available too.