Chemical gear

a lot of people used the fr2($109 in a small store so it should be cheaper in amazon) on the basic and carry the pvc incase they are loading corrosives(that's the only way customers required the sauna suit)

 

I have heard of a cooling vest to be worn underneath the suit. I haven't seen one so can't describe.

 

Search for motorcycle cooling vests or cooling suits or cooling shirts. Some of them are of the soak in cold water then evaporate and some are of the type like astronauts use. Wear a vest or shirt with cooling tubes and carry a small cooler full of ice/water and pump that circulates cooling fluid through your shirt/vest/pants.