A couple years ago, I bought a basic black boonie hat like Fear the Turtle linked to. I found it somewhere online for less than $20. They are easy to find pretty much anywhere.
It has a fairly wide brim to shade my face, ears and back of my neck. And it can easily be washed after sweating in it all day.
My head is also too big for any one-size fits all hats. I was able to order the boonie hat in a specific size to make sure it fit.
Also, you can find them in all sorts of colors.
Another recommendation for a wide brimmed straw hat. Tula Hats has quite a variety. I have the Sierra and I like it a lot.
I came in here specifically to mention Tilley!! I’ve got a large head for a woman - hell, I’ve got a large head for a guy, and they fit nicely.
I got the widest-brim one they make, in a cotton fabric. It’s a bit heavy and warm; one of these days I may invest in one of the manmade fiber ones as an alternative. My husband has one of those and it seems a lot lighter.
Hey, that’s my favorite hiking hat too! Clearly you are a practical person with impeccable taste!
Just go to any big chain drug store and get a big brimmed straw hat. They should be displayed soon. They’re sort of cheap, most have a chin strap and you can soak them in water on really hot days. Toss it at the end of the season. Ubiquitous headgear for outdoor workers in sunny and hot Las Vegas.
I recommend the Sorting Hat from Hogwarts. It’s sentient, and can move at least a little. It’s probably the only piece of headgear that could conceivably operate a mower or set of hedge clippers.
I’ve been wearing one of these for years: Mesh Crown Aussie, 2X-3X (since you say you have a big head, like me). The mesh lets air flow through, but still gives adequate shade. And the hat crushes nicely, so it’s easy to store flat or under stuff.