Check out Classic stairs 3D model on CGTrader for $130. High-quality mesh by klisan: 1062415 polys, 1091623 vertices. Textured.
MAX (Autodesk 3ds Max, filesize: 16.5 MB), OBJ (OBJ, filesize: 740 MB), FBX (Autodesk FBX, filesize: 68.6 MB), STL (Stereolithography, filesize: 367 MB)