I've got the same problem, a large melon. That's why I hate the "low profile" hats, they look like I am wearing a little kids hat.

Imperial Headwear makes hats in larger AND smaller sizes. http://www.imperialheadwear.com/en/prod ... hp?PID=101

Give them a call and they can give you the number of a guy who sells them at a retail price that is not very expensive at all.