It's technical name is the Kit Bot chassis, and is supplied by IFI.
While it doesn't look like there are CAD files you can just Download on the page on
IFI's website, there are prints of all the parts included so you can draw them if needed.
http://www.ifirobotics.com/kitbot.shtml
edit: See below. That should help you. They ARE on FIRST CAD Library after all.