actually, you should be able to strap that to the top of the amp, and cool where the heat is naturally transferring- the heatsink fins. the transistors are bolted/pasted to the main body, not the back cover, so there would virtually be no difference in cooling underneath the amp........on those, there really is only 2 wires connected to the usb connector. all usb is 5v, and so are many computer fans, so keep that in mind. you can find some std. case fans, and parallel them just fine. i have also run 5vfan on 12 supply without issue, other than it was crazy fast/loud for hundreds of hours (ps2 fan)...and many more options in conventional case fans for whatever "cool" factor suits your style. run them off a relay, or remote transistor style relay, for hooking more then the 500ma load to the deck remote.
... oh and "applications they were used for".......well, pretty much all those small cooling fans you see installed in everything from your game systems to recievers, head units, amps, and home receivers, are the very same cooling fans used in computers and lap-tops.