In reply to dek:
Outdoors shops sometimes have stretching devices they can do it for you, the way we do it is drop the shoes in hot water, inside a bag, with the device inside and let them cool. Might be worth ringing around your local shops. One of our customers recently had taken a cast of his daughters foot, cut it in half and put a thread inside it so it could be wound apart and basically did what we would do. Which worked if you've got the time and skills to do it!