I know of a sheet metal mfr. that the company I work for has used for many years. I can pretty much guarantee they would be able to make your tub or anything else you might want. Heck, they could probably make any of the sheet metal for any Bolens ever made, right down to the powder coating.They are A & E Manufacturing in Bristol, Bucks County, PA (north of Philly, about 2-1/2 hours from Littlestown).
Here's their website home page:
Check out this video showing their capabilities:
Of course, the big question is cost. If you could drum up enough interest, maybe you could get the quantities high enough to make it cost effective.