My daughter had the red Elmo one that I bought at a garage sale since I knew she wouldn't hold hands--she's got the 19 month old independence streak going. I just couldn't bring Elmo to Disney--it just didn't seem right since he's not a Disney character. I made my daughter a Cinderella harness instead. I used the white buckles from the red Elmo and used the Elmo one as a pattern, bought 1" and 2" white straps and 2" sew on velcro from the fabric store and embroidered Cinderella's coach and horses on the front of white straps before I put it together. She was SO cute when she had it on with her Cinderella costume for the
MNSSHP. She loved the harness. She would hand the adult end of the harness to whoever she wanted to walk with. When she wanted someone to carry her, she held the adult end of the harness herself. It was easy to take off and put on and it didn't impede her movements at all (except to make it so she couldn't get too far away). The strap is a good length and the loop for the adult end is just big enough that you can slide your wrist through it, so you don't have to actually hold onto it.
I only heard one negative comment about it the whole 10 day trip. Many parents were asking where they could get one. If you get to Disney and decide you need a strap, Disney sells the one that attaches to the child's and parent's wrist. If your child has belt loops, you can loop it through the belts loops so they can't slither out of it (not listed as an option on the package, but it looked like it would work). The stores don't have them sitting out, but some have them behind the counter. I saw someone buy one in a store that is right next to Splash Mountain in MK as I was killing time waiting for my turn at Rider Switch.