Chew necklaces - anyone have a recommendation?

[SneezySnuffaroo]

I bought DS one of these about 4 weeks ago and he's already chewed through it. I was hoping it would've lasted a bit longer.

Does anyone know of any good manufacturers that might last a bit longer, or is 4 weeks about right for a heavy chewer?

On the positive side, he did bring it to me saying it was broken, rather than just swallowing one of the starfish legs!

DS has the dog-tag style one from here which he likes (he's more of an occasional though so can't say how they'd stand up to very heavy chewing!).

occasional chewer