Check out B-29 Superfortress 3D model on CGTrader for $20.99. High-quality Polygon mesh mesh by Iskhafel.
STL (Stereolithography, filesize: 20.1 MB), OBJ (OBJ, filesize: 73.7 MB), FBX (Autodesk FBX, filesize: 18 MB), GLTF (glTF, filesize: 3.78 MB), BIP (KeyShot, filesize: 27.3 MB)