Yellow Mountain Imports
Melamine Double Convex Stones, 7.5 Millimeters (Size 28)
4.0 out of 5 stars 45 customer reviews | 6 answered questions
I think these stones on Amazon are fabulous, perfect size and shape and form. Big fan of melamine (aka plastic) stones here as they do not break like stone or glass, are less expensive when lost on the floor (where stones do tend to go), feel great in the hand (nothing cheap feeling about them to me), and store wonderfully in a plastic sandwich storage container. The single convex version of this for a couple bucks less are nice, too, especially for teaching as they can be used right-side up or upside-down to indicate base pattern versus your moves on that base.
I bought a nice vintage goban (Japanese, real Kaya, four legs, circa 1920) from an eBay seller from out west (Utah? Oregon?) named SailerKing. He lists amazing ones, like now for $750, but every now and again (an auction ended a few days ago) something very similar for about $150-$250 plus shipping. He did a nice job shipping my Goban, has good feedback, and although I do not know him personally, I’d buy from him again.
Having said that, and owning stones made of agate, onyx, Yunzi, shell…I prefer the Melamine ones, to be frank.