Caps-take a look at this case. HHI has a couple of thin cases that are supposed to be dock able in the apple dock.
zCover iPad gloveOne AP1AH Dock-in-Case Silicone Ruggedized Bumper Case, Black
Have not held the "handheld" cover... But unless it is less than 1mm thick there is no way that it will dock... I tried one that is about 2mm thick and the keyboard wouldn't connect or charge