I have made my own cutters from strips of metal glues to a piece of wood scrap.

I used the metal strapping that is used to ship lumber, found all I needed in the trash pile at a nearby construction site. First I clamped a 20" long section to the edge of my work bench and created a sharp bevel edge using a metal file. Then I bent it to shape with needle nose pliers. I mounted the cutter to a piece of wood by setting it in a blob of 5 min. epoxy.