Try looking for a "rondeau", as we call them where I work. It's a big, heavy-gauge aluminum pan, round, and about 6 - 8" deep. It can cover two burners easily, and even four burners, although in covering four burners, not all of the burner is covered by the pan.
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My wife doesn't much like ground meat, so when I use Italian sausage what I try to do is cook it beforehand then cool, refrigerate, and slice it cold, since it will keep its shape that way. So what you could do for your sausage is bake it, cool it, and slice or dice it. That would change it some, and may not be what you or the restaurant want. You could also probably do some of your other things in the oven too if you wanted.
(Though since you specifically referred to mushrooms and onions, maybe you weren't doing sausage on the stove in the first place. And maybe your ovens are already occupied during prep time too, in which case this might not help anyway.)
I use a roasting pan on the stove top at work all the time. You could also use the roasting pan in the pizza ovens. I put those same roasting pans, even the regular sauté pans on the grill, too. Fire is fire, and heat is heat...is usually doesn't matter where you put the pan, as long as all the parts can take the heat.
How can we sleep while our beds are burning???