I got them
here. I had them engraved w/ "If Lost Call Mom (cell) #," and "If Lost Call Dad (cell) #."
We have two kids and I got two for each (so we had a back up in case one was lost, etc) and it cost us about $12 including shipping. They took less than a week to arrive.
FWIW, my 6yo dd wore hers on her wrist but I put 2yo ds' on his ankle! Both worked great!