I have a pretty large head (22 1/2"), and my friend has an even larger (maybe 23 1/2"). Arda makes wigs that are more suited to big heads.
That said, if you ever want to style wigs for a big head, I'd recommend making your own wig head by taking a plaster bandage or paper mache relief of your head with your hair up in the way it would be while you are wearing it. When you style a wig, even if it's a bigger size on a regular foam wig head, the spikes or other detailing will sit weird when you're wearing it.
Guns don't kill people, shinigami notebooks that fall from the sky kill people.