Chew-proof indoor lead for large dog breeds?

My 1 year old pitbull rescue is still potty training and needs to be on an indoor tether to limit his roaming range. Unfortunately he is a biiiig chewer and has chewed through three leads I’ve used. He mostly chews because he is bored I think. Even with access to toys and such, he has to chew his lead.

Anyone know of heavy duty, chew-proof leashes or indoor leads??