Stainless steel pickle wire collar

Then this stainless steel barbed wire collar might be what you are looking for.

It can be used as a regular piece of jewelry, but also as a daily collar.

With its circumference of about 43 cm (at its longest) it fits nicely around the neck.

By means of the short piece of chain at the back you can possibly make it a little shorter (about 4 cm).

It is made of stainless steel, so it is ideal for people with a nickel allergy.