Emergency! Please Help Save This Baby

This baby was thrown from a car this morning. I stopped and picked him up and rushed him to the closest vet I could find. He was freezing and could hardly hold his head up but got bursts of energy to crawl all over me. The vet thinks he may have head and or chest trauma and needs to be at a 24 hour vet hospital on oxygen and fluids and other medication along with x-rays and possibly surgery if the x-rays come back with anything major. I called multiple 24 hour hospitals to get quotes that range from 2500 to 4000. I don't have that kind of money laying around but I think this baby deserves a chance after being thrown from a car by someone who didn't care about him. Anything will help I have to pay the vet he is at now and pay the emergency vet in advanced before they will do anything.  
I would really love to save this baby and keep him we just lost our cat of 18 years last month.  Please share...