More than likely the top manufacturer is GAHH in California. Very reputable company. They use the original "Sonnenland" A5 topping material made by Haartz GmbH (formerly Rode and Schwalenberg) in Germany. Try
www.gahh.com and you can probably find a local distributor in your area that distributes their tops. As far as I know, they are the only top manufacturer currently making a '97-'02 replacement top with a glass rear window. More manufacturers will surely follow but may not use the original equipment material.