Here are some of my favorites I've looked at online along with where they can be purchased if anyone is interested.
And here's a link for a lacy crochet pattern that can be placed over the staves of a folding fan:
And instructions for making a fan out of popsicle sticks:
Of course, a piece of cardboard will do when that's all you have (or you could just stick to the air conditioning or electric fan).
Have a great day!