Hey Poppy,
That looks great! Yeah man, dowels will work fine, I just don't like the end grain of the dowels with the face grain of the shells. Again that is just my anal personality. Do you have a Woodcraft or a Rockler anywhere nearby? How about a more high end tool store. They would have the plug cutter. And if anybody needs plugs, I can cut a bunch and send them out, no big deal.
Lucky