Your first S.A.M isn't missable but the rest are. Following this video guide you will be able to get the achievement fairly easily. All credit goes to clumsy catbird on YouTube.
Edit: According to one of the commenters you can get this achievement as well by simply loading into the last level in co-op even if it's by yourself and it will unlock. I unfortunately am unable to test this theory for myself as I already have the achievement unlocked.