Urgent Help for Knight's Hospitalization

Knight was vomiting, crying in his litter box, and refusing to eat, so I took him to the ER. They found a urethral blockage that would be life-threatening if left untreated. The vet unblocked him using a catheter, but every time they took it out, he would block up again because of the sheer amount of crystal in his urine. They told me he was in extreme pain and said they had to keep the catheter in and monitor him for at least 2 days. As this is a pre-existing condition, it is not covered by health insurance, and I am unable to cover the full cost, which is estimated to be between $3,666 and $5,389. I have called multiple hospitals in the DMV area trying to transfer him to a cheaper place, but no hospital in the DMV has been able to give me a lower estimate. Knight is everything to me and his brother, Buster, and we would appreciate any amount to help pay for his treatment.