Hi,
I'm a new member (Taz 1), though a Z'd owner for some years. Love your Z'd great looking beastie! Noticed you're looking for centre caps, you might try 1972dragon on e-bay, he seems to sell a lot of stuff like that, I've just bought a dial surround from him, quality is good and he seems popular. Hope this helps. Oh, if you give him measurements I think he's willing to make it for you.
Congrats again on a geat looking car, my latest one is still a work in progress.
Best of luck
Taz 1