What you call worry beads, in Greek does not have that connotation. We do not use it to contemplate of our worries nor does it have anything to do with religion, such as rosary have. It is used mostly by people who want to give up smoking, since it keeps the hands busy and in a way the mind too. It is an object used in leisure time and quite often by old people who sit at Kafenion or Coffee shop.
It is called 'komboloi" and it usually has a single number of beads.Usually 19 beads.And the best ones are those made with amber beads, since the sound the beads made striking each other is very smooth.
Unfortunately, the modern ones are made with plastic or similar substances and it has become a trendy item for collection.
Many people collect them and specialized shops selling only that item are popping up all over.