I've recently come across one of these vintage floor polishers from my vintage parents. Thanks for the tip about "snap".
To remove the wooden brush disks:
Place the polisher horizontally on a work surface with the brush disks facing upwards. The brush disk central metal boss sits over the circular drive stub. The retaining spring loaded press stud is in the drive stub and can be see to one side of the brush disk central boss. With, say, a smallish flat bladed screw driver, press the press stud fully in and start lifting the brush disk off with the other hand, loosening the pressure on the screwdriver at the same time.
As to obtaining new brush disks: seems that buying new ones is now not possible, but new wooden brush disks could be wood worked up from larger brushes refixing to them the metal central bosses from the old brushes. The bosses are held on by three screws on each brush disk. A good project for fanatics!
Derek (UK)., July 2019