Hi Nicholas,
I found these... They’re 4hp and 3D printed so they’re presumably pretty customizable.
I hope these are what you’re looking for!

https://www.shapeways.com/product/67YKP7968/eurorack-blank-panel-4hp-vented?optionId=70725951&li=more-from-shop

If the link does not work (not sure of Modular Grid’s rules), just search “3D printed euro rack panels.” The store is called “Shape Ways.”

I have no affiliation with the site posted nor the product mentioned and therefore cannot vouch for them.

Kind regards,
John