I redesigned the bottom part from the IKEA Lack Screw Grommet with Cap by HotTabascoSauce to make a fan mount out of it. It works quiet well and until now I don't have any problems with it.
It's possible that the fan will get a bit louder because of vibrations. But I guess, when you use a good quality fan it will be not very much.
Feel free to share, remix or post a make from it. If you have some questions, leave a comment.
Kaisertech PLA 1.75mm
The holes are made for M3 screws and there are octagonal holes for M3 nuts.
Make a hole of at least 50mm into your Lack table. Then push the pipe like part into it and screw the fan mount from underneath.
I'm using the IKEA Lack Screw Grommet with Cap for the cables. Then I needed a mount for a 80x80 fan. Theoretically you can transform the lower part of it into everything, so I made a fan mount.