You can count on a distiller to give you zero fluoride water. The cost of the distiller, around $300, plus the cost of the extra electricity, is still cheaper and more convenient than buying and hauling big jugs of water.
Another alternative is a bone char filter. Because fluoride loves to mate with calcium, and because bone is mostly calcium, a bone char filter will remove fluoride.
However, a carbon filter such as Britta or more expensive under-the-counter filters do not remove fluoride. The molecule is too small.
Reverse osmosis is said to remove fluoride, but I do not feel confident with this technology.
A deionizer will remove ions, and fluoride is an ion, however, around 2.0% of the fluoride in fluoridated water is HF, which is not an ion, and which a deionizer would not remove.