Dam I feel your pain, hot air in means hot air out.

Monitor the Humidity if you use a swamp cooler but an A/C is what you need, sorry dude. No real quick and easy answer.

I do know of a few who use ICE just under the air inlet and that helps a little but for months at a time that will be a pain in the ass.

For example one medical grower I know has made an ice mold that fits inside his air in duct. He used a 6" inlet but where he put the ice is 10" and then reduced to the 6" to fit his fan. There is a 6" hole in the middle of the 10" x 5" block of ice as to not restrict the air flow but cool it. He only deals with extreme heat for about 2 weeks a year. Just an FYI.