This fan mount is for 30 x 30 x 6,5mm³ fans. You need no screws, just clip in into the mount and clip the holder into the raspberry like you can see it in the pictures.
This mount should probably fit also into nearly every case that is available out there.
Edit: I've also uploaded a 2nd version with the subfix "30,5mm" (printed in RED), which is a bit wider for the "fan"-part. You can see in the "BLACK" pictures on the right bottom one that the fan mount is a bit tilted. If you also get this result, try the "30,5mm" version.
If you like my designs and want to support me, consider buying me a coffee :)