Oberon covers for the K4 are exactly the same as the other 3rd party covers--they are made to fit the K4 Touch and thus are TOO big for the non-touch. Looking at their posted photo there is at least a 1/4 inch of extra material on every side of the K4 NT.
Oberon covers are nice looking, but as @WTSharpe says they are thick and heavy. They are way too expensive too.