Part number for the S3 Estate wiper arm

Can anyone help me with the part number for the S3 Estate rear wiper arm?

It is a 2015 Business Estate. The end of the arm split when the wiper blade supplied proved to be too wide.

The plastic arm is 300mm centre to end and has the locating cut out 270mm. Overall length is 320mm. It takes a 15mm wiper arm insert which is 16 inch long . The arm slldes down the arm on two shoulders and clicks into the cut out.

All the wiper arms I can find have a metal(?) rod at the end which the blade clips into.