Help, Turntable Belt.... Weird

Okay so I called the distributor of my turntable and I had a slight problem with the belt, so anyway they told me to clean it with Windex? These seems a little off to me but maybe I am wrong, does'nt windex have like Ammonia and or other components that could soften or damage rubber?

Anyway, I will clean and Talc it but what is a correct cleaner for this method?

Also they want kinda a lot of money for a replacement belt from them direct, anybody got good cheap online sources for a new belt?

Thanks