1) You can do it with the MaestroTimes font.

In the Default File there is a similar expression, showing two eighths = a (swing) triplet.

You can duplicate this Swing expression (which uses the MaestroTimes font), and edit the duplicate.

Are you familiar with the Text Tool feature Tracking?

2) If you need full control over the layout (= if you do not like the look of the MaestroTimes font), consider making the expression as a shape expression.

In the Shape Designer you have a small drawing environment inside Finale.

Here’s a tutorial I wrote up a while back:

https://www.dropbox.com/s/txr4y9ewnjz8aki/Maestro%20Times%20and%20Swing.pdf?dl=0

I just checked, using the new SMuFL fonts. It doesn't seem to work as well, or, more likely, it's operator error. I'll keep at it, but in the meantime, my instructions for Maestro Times and PopChar are still valid.

Thanks, most helpful!  Somehow I'd missed both the Maestro Times font (was trying Maestro) and the Insert Symbol menu pick.  But even if I'd found them, would've taken a long time to realize that constructing the above pattern would take a dozen or so insertions, placed in exactly the proper order.  (Seems like a product improvement opportunity to me.) 
But now I get the idea, and saved your PDF.

I understand the utility of PopChar, though I expect I won't need to produce such often enough to make it economic (this was the first time I'd done something like this, after several years using Finale).

Glad I could help. In the meantime, I sent the SMuFL problem in to the PopChar people. They confirmed that it didn’t work, and are working on it.