Baboon: ...
The fan on the right is the perfect size, but I suspect that's the 12v one? ...

There is still another similar 30mm somewhere (did not find it yet) which could be 5V

RUKI:

 

Baboon: ...
The fan on the right is the perfect size, but I suspect that's the 12v one? ...

30mm 12V (Toshiba)

 

There is still another similar 30mm somewhere (did not find it yet) which could be 5V

 

Found it. Happened to be 5v BUT - 25mm (by Turnigy) :-)

Have you checked Ebay? I bought one a few years back that just had a USB plug on the end. Its awesome and quiet.