FWIW, years back, when I used to be able to get the Marellis done, my rebuilder couldn't find any brushes, with any ease at least. Instead, he found ones that were close and "cut them down". This worked well. I suspect the metal can be manipulated fairly well. Over time, I don't really recall seeing any out there on the market. So you might consider the modify something existing gig.
As an aside, pay close attention to the condition of the armature. It will "twist", causing the small lamination pieces to come loose, or be possibly lost. At some point, the armature windings can contact the laminations, and cause a momentary short out of the unit. And in many instances, this won't present itself on the bench, rather only under load. If you see the laminations not perfectly inline with each other, (this will be at the front end of the arm), that's evidence of said twisting. Ultimately, I quit having the Marellis rebuilt, as the one place I found domestically to reman the armatures, went out of business. Even when I could get the armatures rebuilt, we were seeing maybe two or three of every ten being usable in a rebuilt starter, and of those remaining, maybe half of the armatures were possible to be rebuilt.
TdF
