Low-Cost Bunny Surgeries?

Hi,
I volunteer for a shelter located in the western suburbs of Chicago, IL. We currently have no area vets that are willing to spay or neuter bunnies at a low cost. The typical vet fee is close to $300 at a private vet. Can anyone help us with this? Bunnies that leave the shelter not spayed or neutered are more likely to be returned due to aggression and other nuisance behaviors. Plus we always fear that people will breed our rabbits after adopting them.