if they're heavy, like you say, chances are they're glass. fmg has a lot of nice glass pearls in bigger sizes. they look like they're 8 or 10mm. i'd order the glass ones from fmg and tell your customer that because those beads are vintage and one of a kind finds, you can't repeat it exactly but that you could substitute nice quality glass pearls in the same size. they'll look just as nice!
