I found a brand new maker of buckshot molds, and made right in my home state! They are a little expensive, but look to be absolute top quality. Check out that cool toggle and gear hinge. It looks like he will make any size shot or ball, even up to .75". I swear, bullet casting has been the worst thing for my savings account.
https://www.youtube.com/watch?v=lPC6YPwfofY