We just visited Kloster Eberbach last week. It is a monastary that produces both beer and wine, located just outside of Hattenheim (about 10km south and west of Rudesheim). I do not know if they import any of their wines and the websites about the Kloster are all in German, but you can get a feel for the place by viewing klostereberbach.com. They have e-mail and would probably answer a question in english.