A while back we ordered a new starter from Euro Moto Electrics.
It weighs half as much as the original BOSCH starter. About 6lbs lighter to be exact.

As a result, it doesn’t require the rear mounting bracket the heavy Bosch starters need (#2 in Photo).
The starter itself has threads where it connects near the flywheel so no need for the original nuts. You simply install the bolts from the flywheel side, and tighten the starter to the engine housing.
I plan on keeping the extra plastic cover and wire ring that holds it in place (#10 and #11). It will help keep some of the clutch dust contained.