You should be able to get coral beads, but the main thing to consider is the source. Coral beads are sometimes labelled 're-crafted', which means they're made from pre-existing coral ornaments and jewellery which have been recycled. Some other coral comes, apparently, from aquaculture operations, where the coral is farmed for the industry, and not taken from natural reefs.
I haven't come across coral beads before, only on pre-made jewellery. If they're difficult to find, how about replacing them with smooth, opaque orange/cream glass?
Look at me still talking when there's science to do.