Well, I can still only see Joshua's caubeen, and not that of Baldybrown, the OP.

I have a couple of caubeens myself. In fact I might consider selling one. The main difficulty is that I really don't know what size it is, because if it were the size it were marked it would fit my head, LOL! It's a British Army surplus one, which for those who don't know means it's green and doesn't have any band or ribbons. I got it from a German eBay trader who gets a lot of British uniform items. The trouble is, I think the squaddies deliberately get them too big and shrink them on purpose. The lining is also missing, FWIW.

The one I actually wear is from J Byous of Savannah, Georgia, and is adjustable in size, because I didn't want to risk getting another one that didn't fit! (And I have a large head)