R.J.
We love the Texas Rec coast guard approved vests... the same one used at Disneyland :)
http://www.amazon.com/Recreation-Medium-Safety-medium-Aqu...
That link I think is to the child medium size... which is what we have for our 8year old. We keep the xxs, xs, & smalls he's outgrown on hand for when friends and cousins come over.
What we love best about them is that they are SMOOTH... so the kids can swim without chafing. 2nd best is that when fitted correctly (aka tightly, there should be about an inch or more of space when the front closes), they also keep the kids warm.