You can make a solar system model out of many types of materials. The one thing you should keep in mind is scale as the planets are all different in size.
How to Make a DIY 3D Solar System Model
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Giant Solar System Model
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DIY Solar System Models
Craft / Making A Solar System – Clara and Macy
22 Piece 3D Solar System Model Kit for Crafts, Outer Space Science Projects, White Polystyrene Foam Balls for Painting and Coloring, Spheres and Dowels Included : Toys & Games
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DIY Solar System Models
Scale Model Solar System resources for informal educators