It's the kind Les Claypool often wears, most notably in the video for "Shake Hands With Beef". He also wore it in his interview for boingboing.
Here's a side picture:
Sorry about the crappy quality.
Here's a clearer one, from the front:
As far as I can tell, it's made of brown leather (or some similar material) and has a short bill.
If anyone knows where I can find one, that'd be swell too.
On a related note, anyone know what those angled, often bill-less hats are called? I've seen them on golfers, on George in the pilot for
Seinfeld, and in a store; the tag doesn't list the name.