Try the on-line shop on this site. They may be a bit pricey (£350 for a cat back steel - add £100 plus for stainless) but they are good quality and cheaper than anywhere else I could find. You won't get much joy from the usual retailers as they concentrate on the more common cars - for obvious reasons. That's the fun of owning an Alfa Romeo
Hi Guy's tried the suggestion from Marlon and phoned National Tyres price £310 for a walker middle and a timex back box the i phoned Ryauto Alfa Dealers and they came back with £267.00.
So why should alfa be cheaper than National Tyres ,it dosn't make sense to me.