The orbital contribution can be illustrated by the electrically charged ball on the carrousel: a charge is orbiting, generating a magnetic field. The field at the centre of the carrousel could be measured by the magnetometer.
Depending on where you put the electrically charged ball on the carrousel (large vs small radius) you could simulate the Fermi contact contribution: for a very small radius, the charge is approximately at the centre of the carrousel / inside the nucleus, leading to an additional contribution to the magnetic field.
The spin-dipolar contribution can be illustrated by the bar magnet: the bar magnet generates a magnetic field that can again be measured by the magnetometer.
If you put the bar magnet and the electrically charged ball both on the carrousel, you could study the combined effect of these contributions to the magnetic field.