It is not obligatory for the du’aa’ of Qunoot to be in the words narrated from the Prophet (peace and blessings of Allaah be upon him); rather it is permissible for the worshipper to say other words or to add to them. Even if he were to recite verses from the Qur’aan that include words of supplication, that would be sufficient. Al-Nawawi (may Allaah have mercy on him) said: Note that there is no specific du’aa’ for Qunoot according to the preferred point of view. Any du’aa’ that is said will serve as Qunoot, even if one recites a verse or verses from the Qur’aan that include words of supplication, this will count as Qunoot, but it is better to recite the words that were narrated in the Sunnah.
Al-Adhkaar al-Nawawiyyah, p. 50