Besides the traditional solar system scaled model, you can use other models to compare sizes of astronomical objects.

For example, the following images were of a scaled model originally made to be the Sun (tiny yellow ball) and the Sun when it turns into a red giant (big red ball). There is a tiny magnet in the small yellow ball and another one in the side of the big red ball to keep them together.

This next model is of the relative sizes of the main sequence stars.

The following is an artistic interpretation of the Milky Way, printed on both sides with cotton batting inside and coated with a waterproof sealer to make it solid. This makes it possible to feel the shape of the spiral arms.