The bridesmaids' could loan them to the bride or could put them on their bouquet. I've seen pictures of badges on bouquets and thought they looked great. It's a very sweet thing to do, and doesn't alter the dress at all. I've seen it with pictures of sisters' badges (aka something borrowed, and a symbol of support for the bride) and with pictures of the bride's and groom's badges.
http://www.pinterest.com/pin/303218987381253362/
http://www.pinterest.com/pin/303218987381305328/
http://sororitysugar.tumblr.com/post...-omega-wedding
http://www.google.com/imgres?imgurl=...ed=0CEUQ9QEwAw