I get them from an ebay with id rossipettags. They are $6.99 with free shipping each. I have on mine:
Her name
our address
on the back:
phone
cell phone
license
avid chip number
You can pick a font and a design
these are the large heart, large star, and large circle.
And of course, these are for boys or girls, depending on the style you choose.
Rossi Pet tags double-sided tags