Allright, it feels like im getting closer.
After some research i found that the Aliexpress price for the AM882 drivers are really good. I think im gonna go with them...

Stepper motors are not hard to find. Maybe ill take Tumblebeers recommendation-link even there...

How much is the PLCM-E4 and where can i get one?
Are there any alternatives with a good price/performance ratio?

Btw, i really appreciate your help guys!