Amazon has them. Type in octagon hammer handle. My dad always liked those type of handles. I have a couple of his hammers from back in the 50's and 60's when we re-modeled the house. I've been replacing my handles with them as I need too
Maybe go to a meeting or 2 and meet and talk with the boys. Like Glenn says, you can lay down some rules and then make up your mind. Bring some stuff you've made to show them.