If you are in the states you can find it on Amazon. If you're in Europe AliExpress has it. It's made in China and mine needed to be honed before it worked that well. Just search for clover disc cutter and you should see the same one I used in the Google image search results. It doesn't cinch down on the metal though so be sure to hit hard the first time so it goes through otherwise it will just emboss the metal.
Oh thank you, the hinge is made out of sterling silver tubing that I made. You can also buy the tubing already made but it is easy enough to make on your own.