Drill rod is fine. But its only putting a hole in leather, and you don't even need steel that tough. Any steel rod will do. The secret is in shaping the point so its sharp enough to punch through thick leather, but not so sharp that the point can stick you easily, or bend in heavy leather. Taper the rod to a point, using a grinder, then files, then emery cloth to remove all tool marks, and make the surface as smooth as possible. Smooth steel offers much less friction passing through the leather, making the work easier. Tandy Leather sells an awl for a few dollars, that will do all you could possibly want. I own one, but also won an awl with an antler handle made by one of my club's members, and put on a Blanket Prize shoot. I believe the rod on this awl is tool steel.