There are many websites where you can buy kits to install aftermarket cruise control. One example is: http://www.nextag.com/automotive-cruise-control/search-html Many of the kits you can install yourself or you can have a mechanic install it for you. They kits run from about $100-$200. You can use the site above or just a do a google search for aftermarket cruise control kits.
Another alternative is to get a complete cruise system with all the needed brackets and wire harness from a wrecked Cavalier or Sunfire from an auto-recycler. I believe the parts are the same from 1995-2005. See this site for a detailed installation guide: http://www.hotrodder.com/kwkride/cruise.html I'll be trying it myself.
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