Kufatec sells this:
http://www.kufatec.com/shop/en/Volkswagen/Golf-5-/-Golf-5-Plus-1K/Audi-AMI/-VW-MDI-Extension
Same guys as your screen name, OEMplus Laguna Hills is Kufatec USA
I just bought one of those MDI extension cables, but not from Kufatec,
mfd3.com sold me one for less than $50 shipped.
And they had it in stock