I presume your bike is non-ABS,i've used an ABS wheel on my S just spaced the disc with washers,the ABS ring looks crap anyway,if i remember rightly it's 4.5mm.
My bike is ABS, but with the later tin ABS ring which is only 1 mm thick. The wider wheel is for the thicker alloy ring. Using spacers is probably the easiest way to go.
I wonder if it might not be worth visiting a local metal workers. They might have some aluminium plate the right thickness, or better still aluminium bar/tube. You might even be able to get one of them to cut out some round spacers for you cash in hand If not, what about stainless steel washers? You won’t need that many if you lose the hub spacer as well
I'd mailed you before seeing this. They're excellent Knowing the exacting specifications BMW seem to work to anything between 2 and 6 would probably work.