Spareshack do a stainless version for not much cash... I've got them on my 4S

I dont suppose you know the correct description or part no.

The Ducati description and part no for the 4s is : plate, 374.1.002.1B
The Spareshack ones are called rear-wheel spindle plates

this afternoon I have realised I need a rear spindle as well as the ST4S swinging arm is wider than the ST4, so I will no doubt be visiting Ducati Wolverhampton or Coventry this week as I will be in the midlands for a few days.