I'm using the following fan, which I purchased for $15 at a computer show:
Super-Thin CPU Cooler
Made in Taiwan
I did some looking and found some interesting stuff relating to the fan.
has a ton of thermal engineering info, as well as some obvious plugs for
This more specific link
shows the specifics of the "Super-Thin CPU Cooler" line.
The fan is kind of whiny when it's behind the RF shield, which is probably
due to restricted airflow. The Lasagna cooler has the same problem in this
application. I suspect the Sunon fan/heatsink may be more available than
the Lasagna unit, but I'm not sure. In any event, it's 3mm shorter than the
Lasagna, so it may come in handy for some applications (taller CPUs?). The
heatsink mounts to the CPU with thermal tape, so there are no clips to get
in the way. I suspect this reduces thermal conductivity to a small degree,
but the stock CPU does not get too hot with the heatsink/thermal tape
Power for the fan is +5V, and it is tapped from the serial port connector,
as shown above. The fan came with bare leads, so I simply soldered them to
the surface mount connector.