Disc rubbing against backing plate

I've upgraded to the front end of my Mk2 RS to slotted discs.
Probem is one of the discs rubs against the backing plate as the slotted disc is much wider then the standard one.
Does anyone know if I can get a 'spacer' (for want of a better word) that goes between the backing plate and the inner bearing. It would need an internal diameter of 55mm and an external no greater then 70mm and would only need to be 2mm deep.
Only other solution I'd see would be to:-
* Machine the discs
* move the subject problem by using a heavy hammer (and transfer it to somewhere else?)
* run without backing plates (but that wouldn't pass a safety cert??)
Any ideas?
Probem is one of the discs rubs against the backing plate as the slotted disc is much wider then the standard one.
Does anyone know if I can get a 'spacer' (for want of a better word) that goes between the backing plate and the inner bearing. It would need an internal diameter of 55mm and an external no greater then 70mm and would only need to be 2mm deep.
Only other solution I'd see would be to:-
* Machine the discs
* move the subject problem by using a heavy hammer (and transfer it to somewhere else?)
* run without backing plates (but that wouldn't pass a safety cert??)
Any ideas?