Does anybody know any pro bono veterinarians?

Two years ago, My family adopted a Newfoundland from a family friend who joined the armed services. Boss has since become a part of our family and we couldn't imagine not having him around, however, he has reoccuring problems with his hind legs, he is only 4 and is full of life despite hardly be able to move. My family is willing to do whatever we have to do to fix his legs, but the surgery is pretty expensive. DOES ANYBODY KNOW OF ANY GROUPS THAT PROVIDE FINANCIAL AIDE OR PRO BONO WORK? He doesn't deserve to be put to sleep, nor live a life of pain. Thank you.