I also have a broken starter. When the original starter (which lasted THIRTY YEARS on this 10hp Tecumseh-powered ancient Craftsman/Murray rear engine rider) finally shattered a couple of magnets, I bought a new (Chinese) replacement. It was all I could find, quick, on eBay.
Two years later, the robot spot welds on the bracket came loose and the starter dropped to the frame, hanging by the wire but still whirring when I pressed the start button (Yes, the keyswitch died long ago and I rewired the mower. I work on it a LOT, being retired on a fixed income.) Now I'm considering carefully (TIG) rewelding those spots, and/or more places (like the bracket edges - farther from the magnets.)
If that doesn't work or warps the case (I do know how to manage heat and warping, but don't know what this Chinese "popcorn" pot-"steel" will do
I'll try migrating the new magnets and armature into the old (VERY sturdy, US-Made) case. I had assumed magnet mounting would be difficult to impossible. It is interesting to note how this previous poster made out!
One has to wonder at this point how good the Chinese epoxy is. But I happen to KNOW those magnets are ALL very fragile, powerful, and difficult to manage even in pieces, inside a steel case, and may not be removable in one piece. That's why I'm trying CAUTIOUS tig welding first.