After the recent rebuild I realised I'd run out of rotor arms so I have a surf for some more. I wasn't expecting Bosch but wanted a 'plastic rivet'.
I found a supplier that had a pattern part for a crazy €1.36, I surfed the Supplier Spareto and the reviews were generally very good. Shipping was about £8 so for less than £20 4 rotor arms. I thought I'd give it a go and a week later they arrived, well packaged and they are a manufacturer that I've used before, 'Blueprint'. A good copy of the Bosch and I'm happy.
See here:
https://spareto.com/products/adn11431-rotor-distributorPicture attached, Regards, Clive