You can also look at this website
http://www.friendsofanimals.org/
You can buy spay/neuter certificates that vets will take as long as your vet participated I think a neuter is $65.
http://www.friendsofanimals.org/snce...tructions.html
The Friends of Animals certificate covers the cost of a routine spay/neuter procedure including a cursory (not full) surgical pre-exam, anesthesia, surgical procedure, waste disposal, day of surgery post-operative care and pain-relief, hospitalization as required, and stitch removal if necessary.
The certificate takes about a week to receive.