Here is what tinkering in the basement has produced. All thats needed is 3/8" copper tubing and few hand tools.

Typical roll of copper tubing. I found a 2" length of tubing with the V broadhead shape cut in is about 125 grains. Cut longer or shorter to adjust weight.
I use screw driver to swedge copper to expand it enough to fit snug on 5/16 shaft. I then hammer end section of tubing flat with hammer and cut in V shape.

I use file to sharpen broadhead .note "copper will not take a real good edge"

This is the one I like best. Should have some stopping power.

This head will slide right on any 5/16" bareshaft.
They shoot great and are very easy to make.