Well my plant is to hopefully buy a growtent such as this one 48"x48"x84" Mylar Hydroponics Grow Tent 4'x4'x7' 100 Reflective Non Toxic Room | eBay
A chest freezer seems like a good idea. A small one such as this one: Magic Chef 6.9 cu. ft. Chest Freezer in White-HMCF7W2 - The Home Depot would fit in the tent and I could somehow figure out the tubing to get the cold air where I want it.