Hi bluemax61, assuming that there are no alignment issues with the pulley/belt, there are several possibilties. Since, you have the alternator, A/C compressor, and supercharger driven by the serpentine belt. If the sound is the idler pulley, it is not a terribly expensive piece, and I don't think the aftermarket offers anything better. Here's what outmotoring offers, and it isn't all that expensive:

Good luck!