In hardware catalogs, they will be called "mast tangs" or "strap tangs", sold in various length, width, thickness and holes.
Check thickness & width of typical installations before buying. ou want 2-3 holes in one end to attach to mast, one in the other end to attach a shroud.
Be sure rivets to attach to mast are SS or Monel, not aluminum, as the shear forces will be quite high.