Jimfmiller If so, what kind? Is it multiple bolts? I have searched around quite a bit but cannot seem to find the answer.
The mount probably has this ring plate bolted to its base. I don't own a ZWO mount, so I am not certain; just based it on photos I have seen.
https://agenaastro.com/zwo-silver-plate-for-tc-40-tripod-and-pe200-extension.html
The ring fits into the top plate of the PE-200 and PE160; the part with the three finger bolts:
https://agenaastro.com/media/catalog/product/cache/c18231696039b1770e5ae3c30ff60414/p/e/pe160-9_1.jpg
https://agenaastro.com/media/catalog/product/cache/c18231696039b1770e5ae3c30ff60414/p/e/pe200_111.png
What you can do is to buy a PE160 (they are pretty much identical, and cheaper than a PE200), remove that top plate from the three pillars (M6 countersunk bolts, with simple lock washers; just use strong 5mm hex wrench to remove).
The M6 bolts are 51mm from the center, and spaced 120º apart.
Make a plate for the top of your pier that has three threaded M6 bolts (again, 51mm from center, 120º apart).
That's it.
This is an example of an interface plate from the ZWO top plate to a 40-8080 aluminium extrusion that is used as a pier.
You just need something similar for your pier, but with something else than the four M8 countersink holes.
That PE200/PE160 top plate is surprisingly well machined (given ZWO's other products). I have actually used three of them as quick-release attachment points to the home-made single fork mount I am constructing for the RST135 and WD-17 mounts, by bolting the ZWO tripod extension (first link in this post) to the rings (the PE160 and PE220 comes with a "free" ring):
Chen
