First post, by MrWeedster
Take a Noctua NFA6-25 fan and cut the four connection points of the backside out of the housing with e.g. sharp pliers.
Then adapt the power connector to the fan, and if it's too loud put the low noise adapter in between.
After that glue it into the existing housing. I used double sided tape.
Cheap and silent
You could also take any 60mm fan