There was an outfit in the UK that repaired and sold new Silver Arrow wheels, unfortunately I don't remember their name. I recommend putting the Google machine to work to try to find them.
According to what I read recently BBS will replace the outer rim on Silver Arrow wheels at a cost of $275 each. The owner of the wheel must have a wheel repair shop verify that the wheel is not bent. Only then will BBS accept the wheel for replacement of the outer rim.
I feel your pain, Discount Tire having done the same thing to my Silver Arrow wheel. I hunted all over the world for a fix. I found out later that www.jagwheeltrims.co.uk holds the tools for the trim rings. I fortunately found Ken at Alloy Wheel Repair 520-730-2390 here in Tucson. He removed the destroyed trim ring (it's glued on). He then painstakingly buffed the surface below it to look just like the stainless trim ring. You can't tell which wheel I had this done to, the result was so good. I can't recommend Ken enough. I had even considered buying a lesser quality Silver Arrow for the wheel to keep my very low mileage Silver Arrow pristine!