1. Sounds absurd to me personally. as
@CANMAN said, some of the worst places in america don't even require that. However below are some helpful tips i have.
Couple things I did that saved me when i worked in LE. Because tbh this isn't a serious problem IMO, i've worn a vest with uniform in 95 degrees with 80-95% humidity countless times, you sweat yes, but its not anything unsafe. The normal Hydration is key, and if you don't mind looking like an idiot when your in-between calls its certainly do able(when i was driving i would roll my pantlegs up a bit, ect ect). I also opened the passenger side of my car windows a little bit, and topped out the AC, allows for the most ventilation. Google says go to coolcop.com. Never looked because i didn't need it, but it might work??
One of them little mini fan/water bottle things... put that in your rig. you may laugh but damn does it help a lot.
https://www.amazon.com/Science-Purchase-Deluxe-Misting-Assorted/dp/B001CUYQKM
Baby powder/talcum powder IS YOUR FRIEND.
Under armor Dri-Fit loose tshirts worked the best in my opinion (dont get black or navy blue if you can help it).
Believe it or not the pants you wear, you will sweat plain and simple, your upper body is otherwise occupied(with the vest), so get very well ventilated pants.
The 5.11 PDU works pretty well, I have never tried any of the ice plates, because i have never needed them.