nosiy air con at idle

Hi guys im new to the forum and would like to pick your brains. I purchased a 1.9 tdi beetle for the misses recently and its a cracking little car but the only issue we are having is that when the car is idling im pretty sure the aircon pulley is rattling which is causing the belt to slip also, if i rev it ever so slightly the nosie dissapears completely and it can be made louder by switching the aircon on and off. my questions are...
1. can i just buy a belt from a model without aircon and bypass the pulley? i know she would no longer have aircon but she is happy to trade that for the noise to dissapear.
2. would it be worth buying a second hand unit or is this a common problem?
any advice would be greatly appreciated