Looking for recommendations on what to substitute eggs for via /r/veganrecipes

Hi

So I'm trying to make a cookie recipe for a vegan friend which is basically peanut butter, sugar, and one egg. Mix it to make a clompy texture to roll into balls and then flatten on a baking sheet.

I was hoping someone could give me suggestions on what I can use as a substitute for eggs in this particular recipe since I'm hoping to keep the consistency.

Thank you!