Nichelle isn't the only one who's made shark teeth charms from scratch. Years ago--long before Rio Rondo offered photo etched charms--I faced the same challenge and came up with a similar but different solution.
I used large plastic sequins for the base material of my charms. These sequins cost less than five dollars at Hobby Lobby and look convincingly metallic. Their only real drawback is that they scratch easily.I used a pencil punch and mallet to make holes in the disc...
and then cut out the charms with a sharp pair of scissors. The plastic cuts easily, but it does take a little practice to get the shapes smooth and consistent.
I don't have a close-up photo of the finished charms on the halter, but you can kind of see them in this photo of Shalimay.
Yet another method of making homemade halter charms can be found on Abby Marston's website. As always, I'm intrigued by all the different solutions to a single tackmaking challenge. Rio Rondo and the World of Model Horse Collecting are wonderful resources, but it's easy to become overly dependent on them. Every tackmaker should experiment with making hardware from scratch every now and then!