Dear Roger,
I think your quickest route would be to find your nearest sheet metal worker. This is something that could be turned out very quickly with the right equipment (guillotine, bender, pillar drill etc). I imagine that 1/8" mild steel would be strong enough. It depends on the weight at the end of the stud. You could also use two pieces of L-section mild steel channel, using the stud + nuts to clamp the parts together at the correct spacing. Personally, I would make one call to a sheet metal work and order up what I need unless, of course, you have the stock materials to hand.
Regards,
Bob