I think it is hard BECAUSE she's so young that it's so difficult. Those leashes would never fly with her either (I think they would just make her angry). And to be honest, she's not that out of control when someone is with her, and if we sneak around a corner she will look for us or come running to "get us". The problem is trying to teach her to stay close without having to chase her down, or teaching her that once we're in the line up (getting ready to pay), that running around is no longer an option. And BOY, will she fight. It's mostly a kicking, squirming, screaming type than it is a tantrum (she won't cry, and will laugh once you actually do put her down), but man... not easy.
Distraction (like giving her something to carry) does work, but only for short periods of time before she wants either something new, or to find her own distractions.
She does understand when we tell her that we need her to stay close (although we have to hold her -kicking and fighting- to talk to her), and she'll start to fuss and ask (in sign language) "please!". We have to say no, then affirm her desire to want to do it (show compassion, understanding, etc), and that does seem to calm her down somewhat, but the "please" followed by sad faces is rather heartbreaking. It takes a little while before she'll submit, but it's the whole "restrain her until she does" that bothers me. But I guess that's to be expected at that age?
Both of us going anywhere with her is definitely for prevention of insanity.
I'll try a game with her (freeze, red/green light, etc) and see if she'll understand it, but I think she might be a bit young for that yet. And highly distractible. lol