I actually got an idea in the meantime, and I asked Bing AI for a solution. So I discovered some rubber mounts that should help reduce vibrations hopefully. The AI linked an amazon link, even though they are not available maybe you can find somethink like this and maybe deduce a solution (https://www.amazon.com/Silicone-Rubber-Cooling-Mounts-Anti-Vibration/dp/B00MPEBVRA).

I think it could lead a solution if we keep searching, but I still think that a more solid fan costruction would be better