G'Day Grant,
Yes, there might be steel stock still available. Not yet checked beyond local suppliers, who can't help. Will still be a while before I am ready to add bumper to chassis, so who knows what may surface in the meantime.
At a farm auction I attended late last year, there were two 6 metre (20ft) lengths of aluminium channel which were an almost perfect match of bumper profile. From memory, there was a 5-6mm difference in height, that I wouldn't have been too worried about. We left before their lot number came up, but I have since fund out that they went for $600 for the pair. Ouch!
Considering the changes I am making to the engine, I could have easily overlooked aluminium for front bumper.