Here are some other EGs that I would recommend looking into if you cannot find a Quadrax:

https://www.modulargrid.net/e/make-noise-maths-white-knobs
https://www.modulargrid.net/e/tiptop-audio-buchla-281t
https://www.modulargrid.net/e/4ms-company-pingable-envelope-generator
https://www.modulargrid.net/e/befaco-rampage
https://www.modulargrid.net/e/xaoc-devices-zadar
https://www.modulargrid.net/e/klavis-quadigy