If you've got an old case you can butcher for parts or some Meccano you can make a bracket that will fix to the PCI card mounts and attatch a large system case fan to it that blows directly over the northbridge. Using a large fan will mean you can run it at 5v to produce very little noise whilst maintaining reasonable airflow.
<b>Vorsprung durch Dontwerk</b>.....<i>as they say at VIA</i>
use a side panel fan that blows in ,over video card ,n/brdge,PcI slots, CPu , rear fans for exh.
if not equipped its easy to cut hole & mount 80-92mm fan