Most are too thick. I have an old R*pha merino base layer I can use.
It needs to be something like this. Left is the standard winter collar thing, middle is how I want it in a scarf format covering a bit more chest like a burner, right is roughly what I think the pattern would be.
Could you just buy a merino scarf e.g. https://www.pureluxuries.com/products/bristol-grey-merino-wool-scarf and chop it into appropriately sized pieces for your requirements?