Where can I purchase the rubber O-Rings that make up the inside of the seat backs on a 1968 Series 1.5 E-Type? There are 20 in each seat back. They have an approximate Outside Diameter of 3-inches and the O-ring is about 1/4-in thick. XKs Unlimited, SNG Barratt, and Original Specification Jaguar Interiors (OSJI) do not carry them.