Seconding the honorific “Mx”. From what I’ve seen, it’s decently well-adopted in the non-binary community. I’ve not seen it much used outside of that community–it seems to be used mostly when someone ‘needs’ an honorific but doesn’t fit into the 1950s list. I’ve heard it pronounced “Mix” and “Mux”. I tend to go with “Mix”.
IRL, I’ve used “Hey, you” and “Yo!” when hollering at folks I don’t know (example, “Yo! You dropped something!”)
Sidenote: As a nonbinary person, I prefer not being given an honorific over being given the wrong one.
Minirant not directed at OP: And omg, if you need to go with a feminine honorific and you don’t know whether the person is married, go with Ms, not Mrs. or Miss. The connotations of the wrong one are just creepy.
Not married and called Mrs=“Hey, you’re too old to be unmarried. Please feel judged about your relationship status”
Married and called Miss=“Hey, you’re too young to be married. Please feel like I don’t respect you as an adult.”
In all cases Ms=“I don’t know and/or care about your marital status and I’m trying to be polite”