Bob Fields Door Seals company has been sold to a company in Texas and they’re back making these parts. https://aerocessories.aero/
Since our doors are somewhat unique, you’ll need a fabric tape measure to measure your door. Once you give them the dimensions they can create a seal for you.
The easiest way to install this seal is to remove the door from the plane, and place it on a table. This is also the easiest way to remove the old seal and adhesive.