**NOTE** If you're looking to make your own version of this dressing, you should check out the recipe I posted back here: Lou Malnati's Salad Dressing Recipe.
Last week, I was in the Elmhurst Lou Malnati's picking up a pie and noticed that they're NOW selling a bottled version of their salad dressing they've called "Lou Malnati's Sweet Vinaigrette". That's the second consumer packaged good they have in their take-out shops - with the first being Lou Malnati's Tomatoes. They sell it in 16 oz jars.
I didn't catch a price, but I did catch a photo of the ingredient list.
Lou Malnati's salad dressing recipe, it seems that there are a few differences. First, the bottled dressing uses corn oil (listed first) and olive oil (listed way down), while the recipe posted in the Tribune back 40+ years uses olive oil. The bottled dressing also has mustard, "natural flavors" and a few different preservatives (Delta Lactone?) which I presume are necessary to make this stuff shelf-stable.
In a pinch, I think the store-bought stuff would be great, but if you have the time, why wouldn't you make your own?