How about something that a cooler would be made out of (use an old cooler or something) and put in like packets or something that you can put ice into. Or, here's a thought, route some hose to the cooler type enclosure for A/C! Close off that vent ofcourse when you are using the heat.

2001 BMW 325i Sport, Stickshift '96 Mercury Mystique V6 *TOTALLED* For sale: Alpine CDA-9811 Eclipse Amplifier Pioneer Tweeters