I would contact a home improvement store or a fence company. I am sorry but I am not sure I know what a "catwalk is". Is it a small balcony? They also sell a mesh fencing material for toddlers to protect them from falling through slats in a railing. You could check baby stores or look under child proof fencing on the internet maybe?
Sorry I'm not much help, but I hope those ideas will lead to something.
Good luck |