Just an update, I bought wool from taobao in the end.
It came combed and felt compressed. If I use it as stuffing immediately, it will feel lumpy.
So I had to pinch abit by abit, separate out into small lumps. That took me like 6 hours to obtain about 230g of fluffy wool.
My original cotton filling was 300g but they have lumped like tiny ropes altogether. Using 230g of wool made my original pillow damn bloated.
Quality is really good. I tot it would heat, not my different from my latex pillow. I believe my reconstructed pillow should last another 40 years.