The scholars recommend saying the duas of Zachariyya
. They can be found in Surah
Ali Imran, Surah Maryam, and Surah Anbiya.
Incha Allah, I will attach a file with the list of duas. Perhaps you can print it, and give it to your friend.
In all situations, the Muslim should accept and be content with the decree of Allaah, even if he is to remain infertile for the rest of his life. It could be that his patience may be better for him than a child. Everything that Allaah decrees has wisdom and a reason behind it, and everything is subject to His Will and Command.
The meaning of these duas are:
003.038 "O my Lord! Grant unto me from Thee a progeny that is pure: for Thou art He that heareth prayer!"
019.005 "Now I fear my relatives after me: but my wife is barren: so give me an heir as from Thyself"
021.089 "O my Lord! leave me not without offspring, though thou art the best of inheritors."
And Allah knows.