You can go to
www.3DContentCentral.com
http://www.3dcontentcentral.com/part...brary/140.aspx
Search for FTC. Most of the Tetrix parts are in the library. You can download what you need in Inventor format.
If you have a copy of SolidWorks, the Tetrix models are located inside of Solidworks in the Design Library.
Marie