Sikorsky S-38 or C-6A 3D model is available on CGTrader for $79. Original author: chipbasschao. Specs: 110111 polys, 71416 verts.
STL (Stereolithography, filesize: 27.1 MB), OBJ (OBJ, filesize: 27.1 MB), 3DS (3D Studio, filesize: 27.1 MB), C4D (Cinema 4D, filesize: 27.1 MB), DAE (Collada, filesize: 27.1 MB), DXF (DXF, filesize: 27.1 MB), FBX (Autodesk FBX, filesize: 27.1 MB)