I was at the Experimental Aircraft Association's annual fly in last week and NASA had a huge display area there with many 3D models of satellites, rovers, and even the space station.
I asked if the files were available to the public and was directed to this site. [
nasa3d.arc.nasa.gov]
check these out and I found some other 3ds and lwo files in other places in the JPL and NASA government sites that can be downloaded.
Have fun.