I have this same problem.

I was advised to use white grease mixed with a synthetic lubricant. It gets rid of the noise right away but the problem is the bearings are wearing because the serpentine belt is too tight. I guess that can happen on its own?

I haven't taken mine in to a mechanic to get iti fixed yet. I just got the problem diagnosed.

Oh and I also read some stupid advise to rub a bar of soap on the belt to get rid of the noise. I guess that does work but is very bad for the belt and engine so I was told to never do that. In case anyone googles the problem and sees the same answer I did.