I just saw a cast aluminum helmet on eBay. Pretty pricey.
Do a search for Boba Fett Aluminum Helmet and you should find it.
HandSchaub made some of those. The auction notes that it was made by HS so I would assume it is one of his. Considering the work put into it, the price isn't as bad as you might think.
It's what I paid for mine directly from HS.
CuteLucca has one for sale in the cargo hold:
They are EXTREMELY rare... so if you're looking for one, I'd get in touch with her ASAP.
Thanks, just left her a message.