Where would be the best ( and possibly cheapest as well) place to get one of thses for my GC?

Is it a wagon?

2 door coupe

http://www.kastleskorner.com/store/images/cuscowrxpstrearbar.jpg

you should try to hunt down something like the above. unfortunately the above pictured is for WRX's. I really like the design of it though, looks really sturdy.

I guess this really goes without saying, but for the cheapest, try to keep an eye out for used parts. I got front and rear strut braces for $50 a piece that way for my GC. People say it doesn't do all that much, but it was cheap, and I figured it couldn't hurt.

Its argueable whether the bars do much or if anything at all. I personally think it does and I'm sporting STi's front and back hella expensive but I'm a STi whore so :p Cheapest look around ebay and www.rs25.com you might find something, most people would sell their cusco's and STi's for like 80-100 before shipping used.