P223700 - O2 sensor replacement part number

Hey all,

So I have the above error code P223700 (Open circuit on bank 1 sensor 1) on my MKIII VRS 2.0TDI. Trying to find the part number for the sensor replacement. Short of going to a mechanic and asking him to get the part number from the faulty one is there any other way to find the number? My mechanic is away at the moment and if possible I would like to have the part to hand when he gets back to have it replaced.

Thanks a lot