My father in law offered me a couple older galvanized 3 gallon waterers (I think they're 3 or 5 gallon, they're huge) he has in his barn. They are OLD and mostly in good shape, not rusted out. They were used when he was growing up and his folks had 200 RIR cockerels they raised for 3 months for meat birds, that was before meaty hybrids were developed. He said all the old waterers needed was a leather flap valve replaced because the old leather had dried out.
Except for the fact I don't want to haul around a sloshing, heavy, galvanized waterer in a freezing Michigan winter for only 12 birds I'd take him up on it. The girls are only going through half their plastic gallon waterer a day now and it's been in the 90's.