Do both

as you said your've already bled the system, you have to realize a 19 year old master cylinder is due to change, not because wear, because the rubber seals are hardened so fluid inside of master cylinder is leaking or by-pass.

Parts is cheap, about 20-30 dollars, replacing is easy - if you have basic diy skills, you'd be able to do it within an hour. After that, you'd need to bleed.

If you done this, you'd be all set.