In 2002 Hermes produced an item which they called "anneau collier bambou" or "Bamboo Halter Necklace". The retail price was $560.00, and according to what sales associates have said, it did not sell well so Hermes never produced them again. Personally I think that was a mistake, and I am a bit shocked that Hermes made that decision especially since they featured it prominently in their little "Carre" tying book printed that same year. The picture below is from the scarf tying booklet.
The only way to acquire one today is to purchase it resale. They sometimes show up on eBay, and of course they sometimes show up at private party tag sales. I have actually found a couple at estate sales. They are not easy to come by. And they often come up as the topic of collectors groups with someone desperately searching for one.
I have found them useful even if you are not into the "Halter look". Some pochettes were never produced as full size scarves and the holder allows you to wear a pochette in a neckline for that layered look. I often like to do this with a crisp white shirt, as show below with the pochette featuring little characters contorting themselves into numbers. (Sorry but as long as I can remember no one has ever known the name of this pochette).