Hi, I would get in touch with the shop you bought them from.
When my daughter snapped the elastic on a brand new pair of Gaynors the week before her intermediate exam - we rang the shop and they put another pair in the post for us and we returned the pair with the broken elastic. That was Dancia in London who were really helpful and luckily they had another pair in stock. We have to be careful with the elastic now though as she has special order Gaynors!
Good luck! x