Sold by the foot, this fuzzy seal is used on many Airstream windows and doors in the 1970s and later. To use it, unravel the string from one side of it and install with adhesive like hot glue.
You will need two lengths for each slot in your insect screen frame. The second photo shows the strips after they are installed from the back side. The third photo shows how they are installed from the front.
Measures 5/8" wide and 1/8" thick.