The older boats had a cast aluminum tracking fin. They are no longer available. We switched to a composite tracking fin a long time ago for several reasons. The main one being a composite fin will break off and do less damage to the hull than a metal one will. Easier and cheaper to replace a tracking fin than to fix a hole and replace a fin.
If your boat has lost its tracking fin the biggest concern should be the surface the tracking fin is mounted on. If water has gotten into the balsa coring it could damage the area quickly. If the mounting area is bad the places the tracking fin are attached may not hold for very long. Fixing the hull can get very expensive very quickly.