Brake / clutch master/slaves are basically a bore with a piston that has seals. Either the seals wear/score, and/or the bore and/or piston. Also another good reason to regularly change brake fluid - its hydro scoping and can cause corrosion.
The place will bore out your slave/master and insert a stainless sleeve so you end up with the same size bore.
Then new seals (and piston if needed) and it's as good as new, if not better as the stainless bore is durable.
It is very cost effective and I have done this on many vehicles, mainly trucks, but concept is the same. If factory parts are pricey, this is good way to go.
If you can get a complete slave for a good price then it's probably easier for you?
Get info on the options then you can make an informed decision.
Cheers