I think the best thing to do now its try to fix the problem yourself so you don't have to buy the vet to do it. I'm not sure if any pet store in your area carry any respiratory infection medicine for ball python. If they do then just give a try. If not just hope for the best, and just making sure the temp is right and just make him feel comfortable and hope he would recover himself cuz ball python in general has a strong immune system but I'm not an expert so hope this help.