i had my starter rebuilt locally here in the Sacramento area. as long as the permanent mount magnets aren't damaged, any quality alternator shop should be able to do it.

do NOT, I repeat do NOT hit it with a hammer to 'break it free' because you can unseat the magnets then the starter is useless.

last time I checked a new starter was $450USD.

try

I live near Cardiff. There are a few local automotive electrical repair shops here. I had all brushes replaced for £10 fitted. The starter motor works fine now.
I purchased my Mikunis from the DOCGB magazine from a Ducati 750 GT. The carbs had been dynojetted and had K&N pod filters fitted. The carbs came with the throttle, cables and choke cable.