MD 180 Turbo Fins - noob here

I recently bought a 2016 Mirage Outback. It has the black MD 180 Turbo Fins. One of them is cracked. I’ve made a couple of phone calls, and have been told the ones I have are obsolete (mine have a square cut out near the top that a small bolt sticks down thru from the drive with a nut on the end of that bolt in the middle of the square. All the black turbo fins I see on line have a connector sticking out of the top of the fin). Does anyone know if there is a way to get your hands on this old type of fin? I’m trying to not spend $230 plus for a kit to upgrade to a newer version. Any help or advice would be much appreciated. Thank you.