Buying A Decent Car For My Son

I'm attempting to raise money to buy a decent used car to drive my son around in. My wife left me a few months back and i'm a single dad now, and she took the nice family car in the divorce. 

I currently have a 34 year old borrowed junker that has no heat, no air, leaks oil and gas, and gets horrible gas mileage. It barely runs and i need something better for my son's sake.

I hope to be able to get a better car before it starts getting cold this winter, it would mean the world to me if you all could help me get something better before it's so cold that i have to wrap him in blankets to take him anywhere.