I am being sent to the master rappel course later this year. Is there a badge that is issued for this, similar to air assault?

None. And guess what; there's far more badass courses in the Army that don't award flair either.

El Oh El ! I was an Instructor for the Air Assault School (and Rappel Master). We had a guy That I worked with that was well beyond Gung-Ho. One of our fellow instructors took the Star and Wreath off of JM wings and glued them onto a set of AAS wings and repackaged them in the box. We had this guy convinced that all you had to do was to document 200 Rappels and after completing Rappel Master school, you could submit a 4187 to get awarded them wings. Good Times!

btw - No there is no Badge.

NOPE!