We seem to have graduated from First World problems to Fantasy World problems.
The cost of adding flouride to municipal water systems is not very high. (I’ve included a statement from the Connecticut MDC, who supplies my water.) The cost to add (and maintain) redundant water systems is very significant.
The idea of enabling individual / family addition of flouride is also problematic, as too much flouride would be toxic, so that’s not going to be a normal thing. (If you want to add flouride to your own water – such as if you have well water, for example, then you could do that, but no one will accept the commercial risk of selling you such a system, because it puts them at tremendous risk for relatively minor gain. You won’t find any sensible business person who will do that.)