Very nice printing. I can’t help with parts sources in Belgium, but there are ways you can make the microscope using fewer of the more specialist parts:
Optics: One of the more expensive parts, and one that can be hard to get, is the tube lens that you need if using a microscope objective in the high resolution optics version that you have printed. The basic optics version uses only the parts from Raspberry Pi camera, which is much easier. It has remarkably good resolution, as in this thread Comparison of a pi-camera and a 20x optical lens.
Motor control: You can of course move the controls by hand which saves on all of the motorisation. Motorised autofocus is rather nice to have, and you can do automatic tiled scans if you have motors. You don’t need a special Sangaboard. An Arduino nano works just the same, using the controller boards that usually come in the pack with the 28BYJ-48 stepper motors. Instructions are: Motor controller boards (openflexure.org)