I had a fan on the side of my case... wires broke on it so now I just leave my case open and it actually runs BETTER and COOLER than with the case and fan still on and working...
What you could do I suppose is just measure the space in front of your case can buy a fan that will fit up in there. Make sure you have a power connector for the fan available. I put in an extra fan and it plugged right into a 'system fan' slot my motherboard .
Reviews | Antec Spot Cool | APH Networks
This is what I got. Works pretty well. Right now I have it spot cooling my RAM. hehe