Fluoride Filter Test
I found some very inexpensive fluoride filters at Amazon. The Amazon product page said that they reduced fluoride by more than 85 percent. When I tested them, they didn't reduce fluoride at all. See the video below.
The filters that actually did work are available here at Amazon (ProPur, 9 inch).
The tester I used is also available at Amazon here, but you might be able to get it cheaper at Ebay.
If you decide to buy the tester, here is a good video that shows how to use it.