What if you took old tagua nut beads like those shown in the photo below (I assume these are tagua nut), drilled out the roundels to create round openings and a void at the core of each, and then colored and petrified the remains using an expedited petrifying technique like this (from the Internet):

How do you petrify wood fast?
It involves soaking a section of wood in hydrochloric acid for two days and then in either a silica or titanium solution for another two days. After air-drying, the wood is placed in an argon gas filled furnace and slowly heated to 1400° Celsius over a period of two hours. Jul 1, 2015