We have the plastic frames for the screens mounted on the bronze ports. When we bought the boat the old screens were shot. We picked up some scrap nylon screen material that our canvas maker provided to us for free. Removed the plastic frames, (held on with 2 screws) and cut the old material out with an exacto knife. Used some adhesive to secure the new screen material on and after it set, trimmed with the knife and re-installed. So far they have lasted about 5 years and still look good.
PSC 34 # 201