Can you guys share part numbers that worked for you?
Stre mentioned ru-2970, but that seems wrong:
https://www.knfilters.com/ru-2970-universal-clamp-on-air-filter?srsltid=AfmBOooR4UgE016NJn3Ptc5VQNAGKF7_CBT zmFa-Lf7HOGamrI9iMZYR
There is this "custom aftermarket bracket" mentioned. Fabspeed sells this:
https://www.fabspeed.com/fabspeed-porsche-911-turbo-930-air-intake-system-1976-1989/
but that kit seems a bit overpriced. (unless someone can convince me it's worth the price)