When I suspect something is being mass-produced in China, I check alibaba.

For around $100 per ton, you can get a large variety of river stones in the same size range as your beads. See example in photo. These were from China. Not sure if they offer free shipping -LOL!

You can also get drilled stones - the picture shows some that are drilled through the thickness. They appear to be rather huge "beads"! I'm sure you could get the same vendor to drill the other way. This vendor was in Burma (Myanmar).

The African traders are selling all sorts of beads that are mass - produced in China, and have been for some time now, so caveat emptor!