I got mine from ebay - £7 for a small and a medium and they are fab!!!
I use them as well as their usual collars as I don't know how strong the fastenings are. They look fine but the ones on their regular collars are really strong and I don't want to keep changing over the ID tags between them.
Not that my dogs pull

but you never know when you might need to rely on a strong fastening!!
They do leads too.