Lyre's makes an N.A. "Italian Orange" that is essentially a Campari substitute. I make my wife a low alc. negroni with that, Lyre N.A. gin, and real vermouth, or mix it with seltzer for something like a Campari spritz. She likes it. Seems reasonable to me from a few sips, but I use alcoholic versions in mine, so I haven't had it enough to have a strong opinion.
I should also note that I'm not a stickler for "real" Campari, and have used various Italian red equivalents, like Select, Short Path Amaro, or my current favorite Forthave Red. They all vary a little from Campari in terms of level of bitterness, sweeteness, and spice but bring the same general flavor. And of course the particular vermouth and gin have a big effect on a negroni too...