May Allah facilitate this difficulty for you. Some suggestions:
1- If avoiding their food causes you unbearable hardships with your parents, then you can eat it, because God has lifted unbearable hardships from us. So you can eat with them when you feel it’s necessary.
2- If you have a creative way to wash the food before eating (when it’s possible) then that could be a solution sometimes.
3- As long as you don’t have certainty that they made the food najes, you can eat and you don’t need to investigate. Maybe your mother wore gloves. Maybe her hand wasn’t wet. And so on. As long as you don’t have certainty it was made najes you may consider it pure.
4- You may refer to another Marja’ if you believe the other Marja’ is more knowledgeable in this ruling.