Call Kansas RV Center in Chanute, KS. This is the repair shop that used to build NuWa HitchHikers, They may have the seal you need.
Or check on the Lifestyle/Carriage forum on the internet.
Ken
Amateur Radio Operator.
2023 Cougar 22MLS, toted with a 2022, F150, 3.5L EcoBoost, Crewcab, Max Tow, FORMER Full Time RVer. Travel with a standard schnauzer and a Timneh African Gray parrot