I made one from a 1" section of 3/4" copper pipe. I slit one side with a hacksaw, creased the opposite with a "poor man's cold chisel" (a railroad spike) and "unfolded" it into two sections along that crease, sawed down the crease 2/3 of the way, then nibbled an "ear" out of the excess on the right half with a pair of tin-shears. cut a curve along the top, and rounded the bottom with the same shears. I took a file and rounded off all the edges. Finally, I set it on a block of wood and drilled a hole in the ear big enough for my frizzen screw. Worked it into shape to clear the frizzen with two pairs of lineman's pliers and some trial fitting.
Looks like something the cat gacked up, but it served. Funny thing is, no one that ever saw it asked me to make one for them. :hmm: