I believe the gun is with the Science Meets Imagination exhibit, which I think is in Australia right now?
Probably doesn't help, but I'll check my visual dictionary book tonight (if I remember)
I may have found an image over at the "Chewbacca Costuming Resources" site. I think this may be the weapon's stock/handle (The part Turfful's fur is covering in the visual dictionary).
Although... looking closer at the ribs and top plate of the body. It looks like there are squared edges instead of rounded one as seen in the dictionary