The source where I purchased mine seems to be out of stock. The item is not even listed.
Once you find the punch, the trick is to make an impression with the tip by pressing so that you get a preview of where the hole will be. Once you have it right, line the punch back up and whack it. Keep the punch straight and if doing more than one hole keep it oriented the same way. If what you find is anything like mine it will be a bit crude and may drift. Two holes drifted in opposite directions may be noticeable.