wearable necklace chain w/ integrated battery holder/switch

I’m looking for design and supply information for magnetic barrel enclosures with integrated battery holder and toggle switch like those seen on this page: aliexpress.com/store/902946/ … s-for.html

in the pictures you will see the pendants change but the clasp/battery/chain is standard and I see them on many web sites for wholesale suppliers, but I cannot find information on the clasp/chain sub-assembly. I would like to use it as part of a design I am working in but have no idea how to source it, and need basic specifications (and possibly samples) so I can understand the connectors, etc.

can you help me track that down? Again, just the necklace clasp assembly and chain, without the ornament on the end.