Check out All planets solar system 3d model Low-poly 3D model on CGTrader for $75. High-quality Polygon mesh mesh by 3dFront. Rigged, Textured, UV Mapped.
STL (Stereolithography, filesize: 55.1 MB), OBJ (OBJ, filesize: 56.8 MB), MAX (Autodesk 3ds Max, filesize: 72.4 MB)