I'm so sorry you are going through this.
The only thing I can think of is to apply for Care Credit. This is what helped me with my RB kitty Taz's kidney surgery. The amount is small enough that you should get it with no problem. The only other thing is to make sure the vet doing the surgery accepts it.
It is just a line of credit, but they always have deals where if you pay it off within a certain amount of time it is interest free.

Care Credit is also good to have for routine visits. I even use it at MY dentist! Since I don't have dental insurance.

Good luck. I hope you can figure something out.