Classic car parts can be tricky. I found many classic Jaguar parts were out of production for a time (filters, hoses, etc.). Fortunately there are some pretty good parts suppliers for classic jaguars to help us solve our repair or restoration problems.
Many of these sell online or over the phone and can also provide valuable insight. I don't endorse any particular supplier, but
I do advise shopping around and being aware of what each company provides.