I bought the monkey backpack from
Walmart for our trip when my son was 2. The stinker refused to wear it so we didn't force the issue but I was a stress-case every time we got into a crowd. I would definitely recommend it if your child is cooperative about it. I also recommend the tattoos and illuminated necklaces as well. All of them are cheap and could save you from a crisis!
Who cares what anyone else thinks? As the prior poster aptly stated, "better leashed than lost". I hate it when a thread about safety (like the one about whether to bring young boys with you into the ladies room or leave them alone outside) dissolves into petty nonsense because strangers think they have a right to tell you how to keep your kid safe in one of the biggest, most crowded environments they'll probably ever encounter. Do these people really think I'm going to base my kid's safety on their opinions? Yeah right.