TeNo Stainless Steel Safe Rubber Necklace- IF SOLD OUT ON SIZE YOU WANT,  YOU CAN PURCHASE THE NEW RUBBER CHAIN:

Ultra Thin Black Rubber Necklace with a steel wire running through the inside for extra durability.

bayonet clasp - 2mm thick
rubber - 1.5mm thick

If length is sold out,   you can also use new rubber chain with new style clasp: