Get some aluminum or copper strips, annealed for softness and just bend them around the chainstay. Then reheat and chill them rapidly to harden them. Chromeplate or silver paint them if you need that effect. Use some low grade locktite to put them on (in case you change your mind).
Gold strips would be much easier to bend around the stays but not good for resisting wear. And why have a chain guard that costs more then the bike.