Quiet Amp Cooling Fan

Can anyone point me in the direction of a VERY quiet fan that I could use to increase airflow over my amp? I know about the Parasound Zbreeze, which is now discontinued and also too noisy. A really quiet version of something like that which sat atop the amp would be fine or even a small circular fan which could be mounted to the vertical pole of my rack might do the trick. Any suggestions would be greatly appreciated.