I used to know the guy who made these for the 4x4 shops. Could get them for $110 each, [I think that is what he sells them to the 4x4 shops for] but have lost touch.
Not sure what you mean by "hardened". The aftermarket tanks are made from a single sheet of 1.6 mm steel which is more than adequate. I dragged my 16 gallon tank over rocks for years before I swapped to custom made "chamfered" tanks, to minimise them dragging on rocks.
A single piece of 1.6 mm is much better than the two plate rust magnet design that LR used.

