Spring steel is spring steel- - - - -there's nothing magical about a piece of spring wire. I would not attempt to replace a round ring with a square-shaped one, but it would take me about 5 minutes to make a handful of those rings once I found the right diameter spring wire, with a radius that's close to the shape of the current ones. I would also not hesitate to re-use the clips, as long as they're not bent or distorted. A final procedure for the really anal-retentive folks would be to drill the yokes for home-brewed U bolts that are retained with nuts and lock washers. Just use a piece of round stock the right size to match the groove size of the bushings, probably a #6 or #8 diameter for a 6-32 or 8-32 machine screw nut.
Jerry