I was looking for a RadioShack Scroll Trackball mouse driver and remembered that the driver was developed by A4 Technology. If you need the driver for either the WWT-5 or WWT-13 series (3 button, 2 wheel) mouse, then both can be found by searching the downloads (the downloads link is in the site map of A4 Tech website). The zip file is the complete installation of this driver. Just unpack it and double click the setup. You will have to restart your computer as usual.
Hint: The WWT-5 is the mouse with the Red tackball and the WWT-13 is the mouse with the Aqua colored trackball. Feel free to contact me if you have problems finding or installing the driver. I have downloaded both versions in case anyone needs them.