Gene, I have some 1/4" copper that may work for you. Drop me a line and let me know your minimum dimensions and I'll see if any of the pieces I have will work. If so I'll send em out.
dclarsen@mchsi.com
By the way, I've used copper for bolsters a few times and I really like it. To get the best patina I've found rubbing with thumbs and fingers for a few days will bring out nice blue and green highlights and prevent the crusty oxidation you can get with copper. It's really kinda pretty.
Dave