You don’t need anything fancy when it comes to pattern weights, they’re weights! The simplest, easiest thing to use are flat washers you can pick up at your local hardware store, the larger and heavier the better. I’d recommend getting stainless, so they don’t leave stains on your precious sewing patterns, especially those tissue paper ones you dug out of an old box somewhere.
These slide around to the edges where you need them, stack like coins in your hand when done and store easily in your notions organizer.
Bonus: if you need a large washer for something you have them, what I don’t know, but it could happen.