For Gargoyle, the aria "Ein Mädchen oder Weibchen" is commonly cited as No. 20, Act II.
The score and pertinent data are available here: http://opera.stanford.edu/iu/libretti/zauber.html.
Die Zauberfloete
Links to Acts 1 and 2 at bottom of page. Midi links also available at the Stanford website. In Act II, scroll down to 20. Arie and find an excellent midi by Bill King as well as the text.
In the opera, the first four lines (Ein Mädchen---) are repeated after each verse.