If you're not overly concerned about seams, quarter sawn faces etc, I'd glue up my own 4x4s and mill them down to size.
I believe real pros would cut four matching 1/4 inch thick quarter sawn faces, bevel the long outer edge and wrap and glue them around a center blank that could be made out of inexpensive wood. Basically they're show fronts, paneling really, on all four sides that hide the edges on the corners of the posts.
If you don't know what I mean about quarter sawn your picture shows an example. See how the left leg is more towards the quarter sawn look, has a nicer grain pattern, than the leg on the right, which is a grain pattern from the less expensive flat sawn type board. Unlike you and me, real furniture makers would never show flat sawn surfaces on a fine piece of furniture. :)