This is a school-led exchange and uniform is available to parents throughout the school year. To request uniform, simply email email@example.com with details of what you need, size and whether it is for a boy or girl. Donations of any unwanted uniform can be dropped into the dedicated collection bin at school.
If they are unable to help, you could ask on the LS12 Uniform Scheme Facebook group. Get in touch with them through their Facebook page (link below) and see if they have the uniform you need.