Pie plate replacement
A google search of Spoke Protector led to several suppliers. The size is based on largest cog. Most however are spec'd by overall dimension in inches not tooth count. There are two mounting styles I am familiar with. One type snaps onto the hub. There is a  difference between freehub and freewheel mounting. The other variety mounts by snapping onto the spokes. I can imagine that you need one that matches the spoke count of the wheel.