The battery fits into a compartment that's slightly larger, so the dimensions don't have to be exact. I think the thickness has to be the same or slimmer though, since the cover seems to press against it pretty tightly.
The picture that Robert posted is pretty much what it looks like. It's wrapped around with some black tape, which I don't really want to take off at the risk of damaging something. The only writing is on the side that Robert photographed.