If you wear out your frizzen a new one is a great way to go, if you can find one that fits your lock.
Otherwise, do what was done in ancient times. That is, reface your frizzen. A piece cut from a wood saw blade is about the ideal hardness. SOFT solder it on & you will not draw the temper.
Reheat -treating should, in my opinion, only be considered if you have a lot of experience with such. That is, if you have made many mistakes and figured out what to do about them.
I say this as a metallurgist having made a share of mistakes on flint locks.
Old frizzens were often made of wrought iron and faced with steel.
You can see the brazed or soldered joint on this one.
This Ryan & Watson English pistol was new made with, I believe, an iron frizzen faced with steel.
It would take a long time to put a deep enough case on a wrought iron frizzen to give it much sparking life. In my opinion as a metallurgist, with some experience in case-carburized steel.