National Geographic isn't selling one. One of the best sources of free maps is the CIA, but their Africa map has not been updated either. Maps.com isn't selling an updated map. Even Google and Bing are not showing the new nation (although I expect them to soon. Let me know when you see it). The British Guardian put out an updated map, but I must say that the coloring is annoying, and it's not easily downloaded. One might expect this lack of maps if South Sudan had been created by some overnight coup. But that's not the case, this country was the result of a treaty signed 6 years ago.... plenty of time to get up to speed. The oddest example is the CIA... the guys who are supposed to be ahead of the curve in world affairs. I'm sure they're not stumbling around today, "What, a new nation?! We better get on this!" So, to reassure the American public that they are on top of things... please, update your maps, CIA.
[My map is only regional, but you can see it here.]