Here is a link to a source for screw-on aluminum racing disk wheel covers. These are typically used on Bonneville Salt Flats racers. I have seen a YouTube video somewhere of this type of installation. It is a little involved as you must remove at least one bead of the tire, drill and tap screw holes in the edge of the rim and re-mount the tire. A competent tire shop should have no trouble balancing the whole assembly for you. (You could mark the covers so you get them back the same way when you check tire pressures)
Racing Disc Hubcaps (Pop-On). Scion Hubcaps, Vintage, Kustom Wheel Covers