I suggest that you wouldn't want to replace just the piston, you should replace the seals and spacers too. Probably the brine valve too while it's apart.
You probably know you can't get the seals and spacers out without the special control valve specific tools right?
Fleck parts prices have goen up a bunch since a piston was $14.00! I've been around awhile and don't know for sure but $14 seems low and I get better prices than most. And UPS has increased more than a bit too, and you're in FL.
Quality Water Associates