I always liked the styling of German helmets from either WWI or WWII. If you're not worried about having a DOT approved helmet I'd recommend searching ebay for helmets from either war, you're likely to find a large size that way.
If you want DOT approved try this site. They have sizes up to 2XL.
http://www.leatherup.com/c/German-Helmets/2/178.html