Hallo Manfred!

I replaced the ZR on my V8 4.2 -92 a couple a weeks ago.
The ZR brand was a Gates, wich is the supplier to VAG company. You should be able to buy it in the most after market sparepart shops. It´s important to replace all bearing wheels and waterpump when replacing the ZR.
Total amount for all the parts, including the bolt for the crank was 470 euro....

Good Luck!

/Jens from Norden....Schweden