I mostly dribble right handed, but I need to also use my left hand.
Does anyone know of a drill the would improve my left-hand dribbiling?
I wouldn't say you need an actual drill ,just practice with both hands every day when you train and over time you will get more comfortable.
I use and have heard Power Dribble is a great tool and help you a lot when focusing on trying to improve handling.
Check them out,
My cousin uses it and he likes it.