It is very good that you are asking for a supplication. God always accepts children’s duas for their parents; for their shortcomings, sins and so on.
Sahifa Sajjadiyya, supplication number 24 (for Parents) has many manners and is very useful. The 4th Imam, Imam Ali as Sajjad Zainul ‘Aabideen says in this dua, that O Allah, give me ability, support, instructions that whatever I can support them and You bless them with special blessings.
Your behavior as their son is important; not to be that of an ignorant person nor that of a non muslim, to show respect in all situations, to take advice from the Holy Quran, Sahifa Sajjadiyyah and other supplications. If you read with translation, you will find many instructions. This way you can practically reform your parents behavior.
In the Holy Quran, Chapter 17 (Al Isra), verse number 24, there is a short supplication, asking Allah to show mercy to them just as they showed mercy and blessings to us, favoured us in all circumstances when we were young, to protect them a sthey protected me, to provide for them whatever is good, reform them in terms of health, mental attitude, faith…..
He will change their hearts.
It is a test for a person when his beloved people do not behave appropriately. This is a chance for you to guide them, be patient and wise and try to implement all these instructions. At least you will feel satisfaction in your heart and this will reduce your stress. Show your humbleness and respect to your parents.
It is highly advisable that you and your family sit and discuss these important topics within yourselves. Each of you needs to learn to make their voice heard in utmost respectful manner.
Saqalain Abbas Alavi