Seen a necklace like this?

[AnotheChinHair]

But in the UK for around £30 sterling silver?
www.ornatajewelry.com/products/cousins-sterling-silver-necklace

Have you looked at notonthehighstreet, they do necklaces with 2 interlinking rings for sisters etc so may have something similar.

www.amazon.co.uk/Billie-Bijoux-Sterling-Interlocking-Friendship/dp/B07G96JZQ9/ref=sr_1_3?s=gateway&keywords=Three+interlocking+sterling&tag=mumsnetforu03-21&qid=1558919425&sr=8-3

www.amazon.co.uk/Sterling-Generations-Interlocking-Eternity-Necklace/dp/B07CRVQPQP/ref=sr_1_8?s=gateway&keywords=Three+interlocking+sterling&tag=mumsnetforu03-21&qid=1558919472&sr=8-8