I am looking for the same, having just ordered a new iPad and Logitech Ultrathin Keyboard.
I'm not sure if there is a case that has been designed for the exact thickness of this combo when attached, or whether I'll have to find a case with a material that is stretchy enough, such as neoprene.
I don't want anything too baggy so there is room for movement, but equally I don't want anything too tight that might over stretch the case.