Heres a program called "Care Credit" which is basically a credit card for the healthcare (people & animals). The vet accepts it, and it's interest free as long as you pay it off in the time alloted (12 or 18 months)... So appliy and get approved so you will have 12 months to pay the surgery off interest free.
CareCredit Patient Financing Payment Plans for LASIK, cosmetic procedures, dental, hearing care, vet procedure financing and more.
I hope your baby gets to feeling better. keeping him in my T&P.