ASC designed and built a rear spoiler as you describe for the 2007 SSR. I believe they were still willing to build them from their molds even as of a few years ago, but they were not cheap. The spoiler on on truck O-YLR is an ASC rear spoiler. You can see the ASC spoiler in the 2007 SSR thread or the one on our truck at the following link: September-2015-rotm-winner-river_rat
You might want to check out Eric at MPD1 he has a new style rear spoiler that is want you describe.
Eric is also a member on this sight EricMPD.
Check out for sale and see a few more SSR items by Eric.