If you're thinking about purchasing one, best price I've seen was around $556 a few months back. Not sure about the part # on the rear deck spoiler, sorry.
I’ve seen a few recommendations for SBS Performance splitters. They have a PP2 style and a little tamer PP1 style. They are only around $200 on eBay. SBS has Facebook, but not a website apparently.
I don’t know how good they are and could only find one picture in the forums, but I’m really considering the PP1 splitter. You might be interested in the PP2 version.