OOH you are a task master are you not. I do have a Dremel with heaps of attachments.....so gouging out a recess in a piece of binding to drop a single mother of pearl dot in there is not beyond me.
I even think that just a straight piece of binding across behind the Nut between the nut and the TRC with a dot in in the middle.
I have some pieces of wood veneer here....and a section of white binding....that I could mount a couple of pieces of the tortoiseshell binding to. Then perhaps cut a TRC from that item into this shape.....