All dice jail necklaces now come with an ADJUSTABLE 20 to 24 inch necklace. 20 inches with a built-in 4 inch extension, so you can clip in wherever's comfortable.
https://www.etsy.com/shop/Sneath
I've been selling the adjustable necklaces at conventions and to retail stores for the last couple years and nothing's blown up as far as I know. The only reason I've kept the choice of 20 OR 24 inch on my Etsy until now is because I had to retake and edit EVERY photo and, boy howdy, some of them gave me a hard time.
That being said, if you, dear reader, ever want a specific length of necklace chain, adjustable or otherwise, hit me up. I assemble them by hand anyways, so it's no problem.
P.S. See how the top chain goes off screen to the left and right and miraculously appears, together, on the bottom of the screen? That's physically impossible. The chain isn't long enough to do that. It's called Photoshop and it bugs me too.