I noticed that my trunk liner was missing a couple fasteners. I ordered replacements according to the parts diagram (C2C3910). These were about $10 each but weren't the correct size - not only was the head larger than the others, the pointy bit was too large for the factory drilled holes.

I came across a Toyota OEM part that was not only the correct size, but also a perfect match for the medium-gray carpet colors. They are also much cheaper at $1-$2 piece and are pretty widely available.




Left: Jaguar #C2C3910
Middle: Toyota #90467-05164-B6
Right: Factory



In case anyone else has some missing rivets and is too much of a perfectionist to use generic ones from Autozone

 

Great find! On my car (2004 XJR), the larger ones go in the trunk underneath the rear/hat shelf.

 

Jaguar seems to use a good number of Toyota parts.