You might check with "Steele Rubber". They have MANY extruded shapes for classic cars. Find a cross section that looks like yours and you can order it by the foot / yard.
I did find the right cross section for my coach door, and it works fine.
Mike in Colorado
2004 Fleetwood Pace Arrow 37c,(Jezebel) Ultra RV ECM / TCM, PPE deep TX pan, Bilstein's, Sailun's & Sumo's all round, pushed by a 2014 Chrysler T&C, on a Master Tow Dolly.