Do you have an auto parts store or even a local muffler shop? They should be able to fab you something for cheap.
If I only had raw materials, I would get come galvanized tubing, slit it down one side and create a cone of proper diameters on each end and then weld it in place. Add some high heat, anti-rust paint to both inside and out and live with it until you get something better in the future.
