From the manufacturer of the turntable?

I got it from sonos but they buy from 3rd party   I do not know who the 3rd party is

Does it say Sonos on the label on the device?

As far as I’m aware, Sonos is a reseller of Pro-Ject turntables. I have never seen Sonos resell a replacement ‘band’, you’d likely need to google ‘Pro-ject turntable replacement band’ and see if there are places that sell them other than Pro-Ject. Or whatever name is printed on the label of the turntable device. 

Search for “Pro-Ject turntable belt”.