Ya know, spacers aren't that difficult to build . . . .. 
They do not have to be cast iron. I got some for a Miller offset disc and the guy that purchased Miller disk's (in Texas) makes the spacers from round pipe and plate steel. The bevel or bell to fit the concave of the disk blade is press to shape. Same with half spacers . . . . .

It's not rocket science - way simpler then what we grew up around (cast iron).