I did a quite of bit a research on this topic and spent like $100+ on a master clutch cylinder. I even made a YouTube video on how to replace it. Long story short, it didn't fix my squeaking. But I now have a smooth clutch pedal. What did fix it was using some moly stp lubricant on the clutch ball point as outlined on the forum link above.
Then you have come to the right place. Updated for 2023 I have been asked though PM by one of our members and I thought I should post this publicly so that it might benefit anyone else that has this problem. You must first understand why it is squeaking and not blindly shove in grease as some...
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I never did feel or see the ball, but I ended putting about have a tub (the one from AutoZone) inside the slave cylinder / clutch pivot ball pouch and using a long screw driver / trim tool to try and get it as much inside as I could. The first day, the noise was still there, but I think eventually the stp moly lubricant ended up making its way to the pivot ball because the noise went away. It hasn't squeaked for months now.
I know some say that you should use a lubricant with a specific moly amount, but the only one out there (I think it was Honda) with the percentage recommend; is the size of a quarter and quite expensive for what you get. Good luck getting that on the spot you need it with the amount that it comes with. So, I just went with the cheap Autozone stp moly lube. I did contact AutoZone and STP to try and get the percentage of moly in their lube, but I never got a straight answer.
Tldr. Push a crap ton of STP moly lube into the slave cylinder pouch.