replacement fan can be purchase from here
http://www.mediasonic.ca/product.php?id=1422903534re but if you dislike this brand of fan and want to try different fan
here is what one of our customer did (and We Quote)
""I took it upon myself to replace this fan with the following quiet one.
Evercool EC8020M12CA 80X80X20MM BALL BEARING FAN, (you can find it on ebay)
It has to be 80x80x20mm or it won't fit right. (most fans are 25mm) It took me awhile to find the one above.
You'll have to manually cut, strip, join the wires together yourself.
Just get some crimp on 22 gauge wire butt connectors. (also cheap on ebay")