Nagauta itomaki

I have a Hosozao shamisen with bone itomaki. I don’t know how old it is, but one of the itomaki broke in two when I was trying to tune the bottom string. (Sorry, I haven’t got the terms memorized.) Does anyone know where I can get a replacement? It doesn’t have to be bone, but needs to fit. Right now I’m using a trimmed-down violin peg. Thanks –

Daniel Musick