If you're talking about the electric blue one with the Hartge badge on the extension that was at Lakeside meet last week that is a palo-uber extension, I couldn't remember name of the company when we saw it.
Palo-uber had a very bad reputation over on Northamericanmotoring forum think company folded.
I believe that if you measure the length of the edge of spoiler you could probably get a lip spoiler off of ebay that would do the job? Maybe something like this 51.5" Universal M3 Style Trunk Lip Rear Spoiler Wing : eBay Motors (item 250614950590 end time Apr-20-10 15:33:48 PDT) or this BMW E92 M3 Style Real Carbon CF Rear Boot Lip Spoiler on eBay (end time 28-Apr-10 19:44:42 BST)