I have never found one. I had to buy this one in a shop in the Philippines. Two are of no interest to shell bead collectors. One of these is the chitons, with their segmented shells. The other is the group of large molluscs that include the octopus and squid.
Octopuses have no shells but the most advanced mollusc.
An octopus is said to be as intelligent as a house cat. They are hung in bird cages to provide lime and salt for birds. Jewelers also use them as molds because they can be easily carved and take heat well when molten metal is poured into them. Shells for beads come from one of the other three classes. One of the oldest and most popular are the dentalium or tusk shells .