Most kids shoes, flip-flops, etc. (especially from Target!) come connected with elastic cord at purchase.
I either untie or carefully cut the elastic cord and save it!
There is usually a good 12-14" that comes with one pair of shoes. And with twins (read: two of everything) I doubt I'll ever need to purchase elastic cord at the fabric store ever again! I love using elastic cord for making button loops. I'll show you that later this week on the latest dresses to enter my girls' summer wardrobe!