www.thewheelsmith.net makes all kinds of steel wheels and finding and attaching dog dish caps like the above post would be easier than what you want to do but given the difference in diameters, you may be able to slide that hubcap into the inner diameter as opposed to going over the entire wheel which would look cool and emphasize the width and diameter. You may be able to attach it by screwing sheetmetal tabs onto the wheel where the cap meets the wheel that grab it like a wheel would.