Question about hat sizes

[draydev1]

I've seen Bev's website with the hat measurements for preemie and baby hat measurements and it's wonderful but I need something visual. So, my question is, what can I buy to visualize that my hats are the right sizes or actually close in sizes? Example: I thought about going to the craft section of Wally World (Walmart) and buyin a plastic lemon and orange since I read that those are good for measuring the size of preemie hats, or maybe a baseball and a softball, or a couple different sizes of kids bouncy balls, etc. For bigger kids, I have a couple of those of my own so that's not a problem. I have live models to measure so I'm good there. Am I making any sense? Any ideas would be appreciated. Thanks so much.