I was able to create a similar symbol using two shapes from existing articulation fonts and the smart shape tool. It isn’t an exact copy, but you can try it. If you like it, you can add the two shapes to your personal articulation library (which I use for pedal markings, etc.).
Bring up the articulation tool and choose “create.” Look for “Finale percussion font” and choose #190. It looks like a chime symbol; as close as I could find to the one at the bottom of the real whistling symbol. Then “create” and choose “Kohinoor Bangla” and #515. It’s a black dot. You may want 18 size as opposed to the default 24 that comes up.
Once you’ve placed these on your score, connect the (two) dots with two straight lines from the smart shapes tool and use the angle shape to indicate the direction to swipe the strings.
As I said, it’s a make-shift solution, but maybe worth a look. Since you want to do this, I’m assuming you’re pretty experienced with Finale. If any of this doesn’t make sense, contact me privately and I’ll try to explain further. Good luck!