When looking for tablet weaving supplies, one might not think that one would wander through the fishing aisles at the hardware store, but this is where you can absolutely find something very useful for your tablet weaving kit.
These are size 3 brass fishing barrel swivels that I purchased at the local Fred Meyer (one of those one-stop-shopping kinds of places that has everything from school supplies to sockeye salmon; food, housewares, office supplies, and more). There were six swivels for $1.49.
To attach them to your weaving, tie the strings for each card on the two ends of the swivel (be sure to use square knots!). Then, as the threads get over-twisted, you can chase those twists to the swivel and it will untwist.
Things to keep in mind–you will need to trim the loose ends shorter to prevent them tangling on neighboring cards, and it’s good to keep them offset from the rest of the knots, again, to prevent tangling.
I hope this is helpful to you and your continued weaving success!