Once your dog eviscerates its toy and the squeaker is either pulled out and lost or punctured, you can get inexpensive replacements here
You can also make inexpensive dog toys with old socks-- put a few squeakers in the sock, and sew the top closed. Don't use socks if your pup is young and is still learning what's legal to chew and what's not! You can also sew a tube for this from an old towel.
If you make it the right size to insert an empty plastic water bottle, your dog will also enjoy crunching that flat.