Bought mine when my now 5 year old was 6 months old online from etsy but have no idea who. I loved it and so did the kids. Make sure you get one that is made for infant teething and very sturdily made. You don't want it breaking. Mine was used by both my kiddos and my daughter now has it in her play clothes.
Instead of those teething rings/necklaces, why don;t you use the stem of broccoli or cauliflower or something like that. If it breaks, there will be no harm to your child. I hope you find the answer you want.