The cases made for the original 7.0 will not work, the holes will not line up properly. The cases that are made for the 7.0 Plus will work with it, the only difference between the 7.0 Plus case and a case made specifically for the Galaxy 2 7.0 is the camera cut out. The 7.0 plus case has a cutout that is sort of egg shaped to accommodate the flash and camera lens. The Galaxy 2 7.0 only case has a perfectly round cutout since there is no flash on the rear camera, just the lens.
You'll notice that the 7.0 Plus case on the Galaxy 2 7.0 device may be a little "tight" as the Galaxy 2 is a bit thicker but it still works.