Leather washer for MKIV, MKV or XK120 tyre pump

I make out the ID of the jack body as 1-11/64", so you might try a rubber cup for a brake wheel cylinder with 1-3/16" or 30mm bore. Napa Auto Parts carries wheel cylinder cups, part UP4600. You would have to put a hole in it and maybe use a larger flat washer on each side to support it.

Here is the color of my two jacks. I had the original color matched by a paint shop.
tools 040
We have discussed jack paint many times on the XK forum.
Here is a link to one of those times.