I'd like to add, that a light weight tool helps a lot with "feel" when grinding laps. Therefore the pneumatic die grinder is way better than a heavy electric tool.
Light weight and a small disc make for easy precision sanding.
A fresh 3" 'Rol-Lok' disc can fit most any drill and works fine for removing high spots and goobers. I have a right angle drill I use with the rubber backing disc and am pretty happy with it....
Sorry... don't think I can help you on that. Check the machine's specs for thread size and type and search.