You pretty much have to make one custom, with a heater core in a cooler or something. Rob has made one for the trunk, I can't go into his set-up, so I'll explain mine.
I cut the side off my washer fluid tank, and added a heater core. Then re-epoxied the tank back together. Instead of adding ice, I keep 2 jugs of washer fluid in a cooler with dry ice for the track. I pour it in before running the car, and drain it after the pass. I unfortunately haven't run better with it than 13.2, but that was in 80 degree heat and my pb back in July. W/o it in 50 degree temps I ran a 13.3, but there was a strong headwind. I currently have it unconnected since I switched to bigger IC lines and have to re-do it. From what I saw, it really helped keep the IC from heat soak.