A neighbor hit my car and did not want to get insurance involved, now he wont pay for the repairs what can I do?

My neighbor backed into my car with his truck and I saw it happen. He then took off. I waited until he returned home to confront him about the accident. He told me he had insurance, but would rather not get the insurance companies involved, and promised me that he would just buy me a new bumper and help me put it on the car. Since we had been neighbors for years and we had helped each other out on several occasions, I agreed. I told him I would find a new bumper and he could pay for it then help me put it on. I found a replacement on ebay for $100 and told him about it. He agreed to pay for it. After four months he continues to make excuses about paying for the bumper. At this point when he see me coming he runs in his house and then wont answer the door.