Here are some ideas, maybe you can add a few? I already have a special vest that stays wet longer than other fabrics but I think I might need more. Also, not wearing my padded jacket and pants or helmet are really the last options! I love my life, my brain and my skin too much for that and all of them have vents. My pants even open all along the sides to let the air in. And truck drivers honk at me when I pass them...
* soak the removable foamy parts of my helmet in cold water and put them back inside the helmet before I put it on
* soak my merino ski mask in cold water and put it on
* fill my seat cushion with ice cubes (no, I won't post wet panty pictures)
* soak all my clothes in water
* fill my camelback with ice cubes
* fill my camelback with hot tea
* fill my camelback with hot coffee
* fill my camelback with iced coffee
* fill my camelback with margueritas (there were some laws that prevented me from doing that, wasn't there? Too bad...)
* place zip lock bags with ice cubes in my jacket and pants
* put ice cubes in my gloves and boots
That's all I can think of so far. I already feel much cooler :-). Open to hear your ideas.