If nobody on the forum is selling one, you can also search ebay.
There are several ways to know if the car had the Pioneer system. First, if there are photos of the car, look for a car that had a sunroof. From what I understand, all Cruze's with the sunroof had the sun and sound package. Or look to see if the car had the center speaker on the dash.
If you can get the VIN number from the car then you can enter it into a site that tells you the codes for a car based on the VIN. You can ask the seller for the VIN number. It takes a lot longer, but you will eventually find one. That's how I did it.
I used this site. You can punch in the VIN and then look to see if the car has the center speaker or Pioneer amp listed in the parts available. https://www.gmpartsgiant.com/