I think someome here on IAp is [was] selling those. Seems like $35.00 each. I've also seen them on Ebay & I think it was him. You might check Ebay under"pen blanks".
I've made seven in upper end pens and have sold all but one over the last several months. They need story telling to sell whereas as George said tru-stone sells much better for me.
Well, I have ordered some trustone. I thought I'd try a quarter block of mother of Pearl and black mother of pearl. I wonder how those will sell when I get the material and get them made.