Motorhome Window seals

Hi, we have just had a window replaced in our Autosleeper van and also wanted to replace the rubber seals to all of our opening windows as the van is now 20 years old. The guy doing the works is having trouble locating seals using his usual suppliers.

The windows are Cara Press who I assume are no longer in business, so wondered if any members out there have had the same problem and if so how they got around it solved it?