What to use for binding instead of egg?

So I tried to make croquettes (watched Kill la Kill and decided I needed to try them), but they all fell apart while frying them. Basically I used mashed potatoes and veggies, balled them up and coated them with Becel vegan margarine, flour and breadcrumbs before throwing them into the oil. I understand usually your supposed to add egg to the mix to bind but obviously I'm not using egg. Is there anything else that will work, I'm feeling pretty discouraged.