You could try to find one of those "cooling pads" they sell for laptops. They basically blow fresh air under the laptop. Maybe that would suffice, but then of course you don't really have portability.
Short of that, you're left with tearing the laptop apart to find the fan. Keeping in mind that the fan needs to be of a certain type. Good luck getting a part number from Compac, but maybe you can find a 'puter shop that can find out the number. These laptop platforms often wind up being used by more than one brand. Anyway, you'll need the part number and try to find one just like it.