You can get a 119 gallon bladder tank and run it from 20 to 40 psi for maximum available drawdown within the pressure setting range.
Since you have such a small pump, you can get even more drawdown if you set it up with 18 psi precharge as you would for a 20/40 pressure switch setting, but set the pressure switch at 30/40, or 30/50 if the pump will handle it. You will start the pump sooner (at 30 psi), and store more water, with that arrangement. But you won't run out of water until the pressure reaches 18 psi.
You will have plenty of cycle time because your pump has such low GPM.