I have a 700mhz slot load and it gets extremely hot. The problem with adding a fan is where do you draw power from? Are there any extra pigtails coming off the power supply? I wouldn't think so. The best you could probably do is find a fan big enough to place over the carry handle where the hot air exits and set it up to draw out the air from the outside rather than push it out from the inside using an external power source.

Oh, BTW, with all that heat being expelled directly onto the handle, I wouldn't try carrying it without having at least one hand securely placed underneath at all times. Heat + plastic parts = brittle. The handle on mine creaks and groans under the full weight so I just lift from the bottom with both hands. Better that than having it hit the ground and smashing the CRT.