Lokk in Ebay for military button or google, you will find loads of them. I use button as stopper insert regurarely. I use glass button, they look great.
An exemple of military button found in ebay
I didn't mean to insinuate you broke any rules (I don't think you did). I just thought your topic would also fit in the other forum and might be seen by more people.
I've been finding military pins about 1" diameter and fridge magnets about 1-1/2" in diameter on the stands by the check out at Hobby Lobby. Marines are hard to find though.