The Norse legend of Jormungandr, the 'Midgard' or World Serpent is the greatest ouroboros.
An antiqued pewter pendant, Viking-style serpent-dragon biting it's own tail, making the form of a ring, and engraved on the front in runic and on the reverse with the serpent's names.
On a black cord which is adjustable by a black pewter slide fastener, up to 26" (70 cm) overall length.
I didn't know how to feel about this shop at first because they're cheap. However the products are legit and they're listed as an official seller with Alchemy. The pendant I bought has become a firm favourite