Janneke, maybe they will ship one to you? I know that WWW won't deal directly with owners, but maybe some of the vendors/stores that carry them will be willing to ship to you?
Wizard, they usually use those collars for whippets and other sighthounds because the head is very narrow and not much bigger than the neck. Collars easily slip off so they often use a martingale style. Also they make them extra wide so they don't cut into the dog, it makes it more comfortable since they tend to have longer thin delicate necks. They're not heavily muscled like other breeds. And if they pull like Basenjis, it's good to have a wider collar to spread the pressure out! 🙂 Less likely to damage the trachea.