I'd actually prefer to get the spoiler off rather than adding a diffuser. It was there when I bought the car, didn't think it would be so difficult to get off cleanly since there were no bolts.
I was originally after Jade R, as far as I can gather manufactured by Team Dynamics, but sold under several different brands:
By the time I got around to placing an order it seems they had stopped making the 8" model, I could only get 8.5" and delivery time would be 6+ weeks. Also, one of the dealers I spoke to said he wasn't impressed by the quality.
I ended up getting a set of 8" Ronal (who manufactures BMW's wheels) 41t:
They looked almost like what I was after and the price was pretty good too, so I figured I couldn't spend more time and energy looking.