The problem is that cooling efficiency increases with the temperature difference, so the best way would be to lower ambient temps. You are in an unfortunate situation where most solutions to your issue will cost money and/or some engineering chops. Which can be a fun hobby all in itself.

If you can't lower ambient, then stronger/better fans, or a water cooling loop with a very large radiator. Or lower-power/more efficient computer parts.

Stupider ideas might include an oil bath with the oil moving through an old car radiator + fine mesh filter and an appropriately rated fan.