Buy a Kensington Saver (or similar) cooler (which is powered separately from the Mac).
Install an exhaust fan into the case, taking careful note of its power-requirements vis-à-vis the Mac's analogue-board capability.
Train the airstream from an electric fan across the top surface of the Mac.
Make a passive-ventilator chimney of cardboard, to aid the convective cooling built into the Mac.
That you are starting from a high ambient temperature is a disadvantage, so, if you cannot lower the ambient temperature, higher throughput of air is your most obvious response.
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Install an exhaust fan into the case, taking careful note of its power-requirements vis-à-vis the Mac's analogue-board capability.
Train the airstream from an electric fan across the top surface of the Mac.
Make a passive-ventilator chimney of cardboard, to aid the convective cooling built into the Mac.
That you are starting from a high ambient temperature is a disadvantage, so, if you cannot lower the ambient temperature, higher throughput of air is your most obvious response.
de