Check out Wood Stair 3D model on CGTrader for $15. High-quality Polygon mesh mesh by cgdm: 143144 polys, 146936 vertices. Textured.
STL (Stereolithography, filesize: 63.6 MB), OBJ (OBJ, filesize: 63.6 MB), MAX (Autodesk 3ds Max, filesize: 127 MB), 3DS (3D Studio, filesize: 63.6 MB), FBX (Autodesk FBX, filesize: 63.6 MB), C4D (Cinema 4D, filesize: 63.6 MB), LWO (Lightwave, filesize: 63.6 MB), DAE (Collada, filesize: 63.6 MB)