With the latest versions of Z-Suite software it has been added support for 0,3mm and 0,6mm nozzles, but where are they sold? How can I buy a 0,3mm nozzle for the M200 Plus?
The 0.3 and 0.6 mm nozzles have been available via Zortrax Store for a while now.
https://store.zortrax.com/pl/parts-and-accessories/nozzle-set
You can also ask your local reseller about availability of these products.