Sanlin is not a district, but Sanlin Town, Pudong New Area. There is a professional agency in Dongsanlin, which is Sanlin Expo Home. There is a Sanlin agency on the study road, which is free of charge by the government (only for the local hukou). If the non-local hukou is in Lingzhao Road near Lingyan South Road, Sanlin Town, there is an agency here. You can go and have a look. (I live in Sanlin, and I don't think those intermediaries are reliable enough to be true, but I can make a note. )