[PeterM]

These may help.

https://www.altairastro.com/piers-93-c.asp
https://www.baader-planetarium.com/e...vx-mounts.html
https://www.deepspaceproducts.com/pr...tron-avx-mount
The above are not cheap.

Also found this
https://astromart.com/forums/astrono...xtension-61098

Phil at Pegasus Piers in Qld maybe able to knock one up.
https://www.facebook.com/pier1engineering