Before you start this project, I would buy a replacement frizzen for your Musket. Once you have it in hand, then get yourself a 1/2" x 6" Ferro Rod. Put a heavy piece of leather around the rod and put it in a bench mounted vise with about an inch and half of the rod protruding up from the vise. Make a small mark as close to the center of the rod as you can across the diameter of it, and then move the hacksaw to the right a heavy 1/16" of an inch. Slowly start splitting the rod until you have made a cut just slightly longer than your frizzen is from top to bottom. Cutting SLOWLY helps to control the sparks. Repeat this process on the left side of the center mark. Once this ripping is done, crosscut to the length of your frizzen. If the frizzen on your musket is wider than the piece of Ferro Rod than just leave the piece of rod as is but if they are close to the same width you can shape the piece of Ferro Rod to match the shape of the frizzen, but it isn't a necessary step. Next take a small triangle file or the corner edge of a small flat file and make several scratches across the frizzen and then with a small piece of 80 grit sand paper sand it just a little bit up and down the frizzen, perpendicular to the file marks. Mix a small amount of JB Weld and smear a thin coat of it on the frizzen and glue the piece of Ferro Rod to the frizzen. You can clamp it in place with a small C clamp or probably even a couple of clothes pins. Let dry for about 24 hours. While it's drying, you can take a 1" inch wide piece of 1/8" or 1/4" thick flat bar steel and cut a piece of it to roughly the length of one of your flints. Perhaps just a little shorter. Grind a beveled edge on it at about a 45 to 50-degree angle and then heat it until it is glowing a nice bright orange with a 1 pound tank of Map gas connected to a small soldering torch and then drop it in some water. That'll make it more than hard enough to throw sparks off of the Ferro that you glued to the frizzen. Bear in mind that Ferro Rod is a lot softer than Flint and Steel, and this process is going to have to be redone a lot sooner than later. If historical accuracy is not one of your major concerns, then this will throw some great sparks.
The End : )