CC How about a flanged brass tube insert? You can tap it for internal threads or use a push-on emblem speed nut to attach inside the freight car. These are Weatherhead part number 2030 X 4, 1/4-inch OD and used to reinforce 3-8-inch OD nylon air brake tubing, but they are also available in 1/8-inch OD for 1/4-inch OD tubing as part # 2030 X 2. Available at most NAPA parts stores.
