I just got an update from DM-Toys and they now have a selection of small coreless motors and accessories in stock. That includes 6, 7, and 8mm diameter motors (single and double shaft), sleeving tubes/adapters, flywheels and even worms.
These motors are not industrial quality like Maxxon or Faulhaber. They are similar to the coreless motors model manufacturers (like Kato, Arnold or Bachmann) now use in their models. The prices are comparable (or cheaper) than the replacement Bachmann or Kato motors.
See
https://www.dm-toys.de/en/list/manufacturer/MicromotorEU.html