Your best bet is to move.
Failing that, here are some ideas that may be able to help:
Do you need air conditioning?
It may be sufficient to augment air flow. A typical breezebox fan (2 foot square) will move between 3000 and 6000 cubic feet of air a minute. A 1000 square foot unit has about 8000 cubic feet, so you are getting an air change every 1-3 minutes. Note that to do this, the fan has to fit the opening snugly so air doesn't cheat and go back round. Easy to do with cardboard and duct tape.
Do you need to air condition all the time?
Since the house doesn't store coolth during the day, can you put the AC on a timer and turn it on an hour before you come home? Depending on the unit, you may be able to use a smart thermostat, and set it up to not start until 2 p.m. try to bring the house down to 95, then at 3, try to bring it down to 90, and at 4 down to 85. This way on not so hot days, it doesn't run as much.
Do you need to air condition everything?
Summer doesn't last forever. Is it reasonable to wall off all but one room, air condition that room and live there. Mind you my understanding is that Oklahoma winters aren't great either. This may be as simple as hanging shower curtains at doors, and putting phone books over certain ducts.
Temper the changes with thermal mass.
If you have access to the utilities you can do this:
Buy containers. Used barrels work well. Fill them with water in a basement room. You need significant numbers -- 20 barrels. You can stack them 2 high, so 18 barrels would fit in just over a 6 x 6 foot space. Fill them with water.
At night you pull in cold air run it past the barrels and send it back outside. In the day, your air conditioner pulls air from beside the barrels. Your AC then is at least starting with cooler air and doesn't have to work as hard.
Note that if you are in a humid climate the barrels with have condensation on them. Not a big issue of they are in the laundry room on a concrete floor with a drain. Bad idea if they are in a carpeted room. If the AC unit is outside, you may be able to keep the barrels outside too and do some form of clever ducting to guide the air.
Can you paint the roof white?
Here we can get waste paint form the recycle centre. After checking for lead they sort into water vs oil base, and then white, offwhite, and dark. The paint then is sold in 5 gallon pails for about $10/pail. If you have standard asphalt shingles, then you want oil base paint. On a day the roof is dry, roll on a coat of white paint. The paint won't stick that well. Probably have to repeat yearly.
Can you cool with water?
Can you set up an intermittent sprinkler system that keeps the surfaces that absorb all the heat damp. Irrigation companies will sell you a timer that can be set to run 10 seconds to several minutes at intervals of a few minutes to several hours. low pressure fog nozzles run a few gallons per hour each.
This will not make the house cool, but it may make it less hot, and reduce the load on the air conditioner.
Mist nozzles can make outside living more reasonable too.