I think historical buttons ( or reproductions) from uniforms no longer in service might be a nice touch, though older buttons are often a little large. The Military College of SC ( aka The Citadel) has great brass uniform buttons featuring the SC state seal. Very similar buttons can be had as blazer buttons from various sources. If you have an affection for or affiliation with some unit, it might be good to see what is available. If not, there are hundreds of anchor / shield buttons around. Like choosing a tartan, it is always a good idea to at least have a story for the inevitable questioner.