I've purchased a couple spoilers from JC Whitney over the years. They are the type that have a flexible rubber skirt attached along the bottom. There's one mounted on this car (although it's not a clear picture of the spoiler):
I am considering a body kit for my street car, leaning towards this style:
http://www.performancefiberglass.com/pfiat.htm
Every once in a while I go to Paul Stolze's web page to look at different race cars with spoilers:
http://home.austin.rr.com/ssr/X19RacerGallery.html
I like the look of the one on Mike's car, too. If anyone discovers the brand and availability, please post it here.