Ergotec has a number of steel and even stainless steel handlebar models and they offer Safety level ratings for each model. That being said, all of their Level 5/6 models are aluminum mountain bike models.
I have mounted an inverted Stuttgarter handlebar in stainless steel, as it is close to an inverted North Road handlebar, on my girlfriend's bike and they seem to hold up just fine.

You could also consider switching to a different stem like a Nitto V4 stem with two clamps.