Why not put a post in the LAF Wanted section.
There are heads wearing the Sallet on the Perry WoTR sprues.
Aomeone might have a few left over.
Also GW did a number of Empire heads wearing a Sallet, ranging from the simple one depicted in your pic to fantastical ones.
I'm certain there also must be other places to pick up a good sallet head that I don't know of.
Good luck.