[Cube] cooling fan for 450 MHz cube

[Andrew]

It's hot here in southeast michigan (low 90s) and I just noticed that 
the oh-so-scientific dial thermometer that I stuck in the top grill of 
my cube was registering 120 F instead of the more usual 110 F.
So I grabbed a small muffin fan (50 mm?) and set it on top of the grill 
and the temperature dropped to 95 F.
I guess I have to admit that a proper cooling fan might be a good idea.

I understand that there is already a fan power connector built into the 
cube.
Is there a special fan I need to fit my cube (and it's connector)?
Can I make the fan switch on when the cube heats up (and off when it's 
cool)?

Thanks

Andrew in Ann Arbor
technology is the answer, what was the question?