For those still looking for an OEM-type rear diffuser for the msport 335, I came across this company in Taiwan.
http://www.ebay.com/itm/151159833367...84.m1423.l2649
The price isn't bad, although I still can't find any reviews regarding fitment even they say its based off a OEM example so perfect fitment. They're also offering a full cf diffuser of the same one which is just finishing production for December shipment.