I do not blame you one bit. $150 for a U.S. Helmet?, that is getting a little "outer limits", how many millions were made? Best advice I have is to check out antique shops, flea markets, etc. and odds are you just might stumble onto one at a good price. It might take a while to find one that is not too expensive, but they are out there for sure.
The .303" Ctg., Helping Englishmen express their emotions since 1888.