I believe it is from the AC compressor at it is connected to the AC condenser. It has a sticker on it that says "Calsonic Kansei" with a part number 918 000 5C900 45010.

To all folks who replied, I really appreciate your help. I have no experience dealing with AC compressors at all. And since the car is not drivable, the only option I have is to repair it myself or have someone to do a home service, which would then of course cost more money.

I can just buy a used compressor on eBay, but I couldn't find a thread or video on how to replace this thing. I can unscrew everything and take it out, but I'm sure there's more than than and it might require some special tools.

If it's complicated to replace just the pulley for this particular model of compressor, would it be more easier to just replace the whole thing?