The Falcon fan is 12 volt, size 40mm x 10mm. I just found a "silent" replacement model called the Scythe Mini-Kaze from performance-pcs.com for $4.95 plus shipping. Here's the direct page link:
The airflow may be slightly less than the original Falcon fan, but like another poster said, it's not that critical unless you're working in the Sahara. Silence is golden.
