Michael's last example looks like the way to go. However, there is a slight problem. You can build an airfoil cross section using conic curves and sweep them. But a fin has no tip or root (like a conventional wing) so you have to decide where those are going to be. Then you will have to fill the top and bottom surfaces with a non airfoil cross section surface. Your shape is like an upside down version of a older type tail fin. See if you can find an example, say pre ww2.