If it's not available yet it will be in the near future. Have you Googled? A hitch is almost certainly available from European suppliers, because trailer towing is very common in Europe.
Present - '06 E90 330i sport; Past - '04 E46 ZHP, '00 E46 328i
www.bmwcca.org member #388003 - Use me as a referral & you could win a one day ///M Driving School!!