In case you're in need of a larger Grow Chamber, here's some additional ideas: 
Here at AZMGA headquarters, we've had pretty good luck using old commercial refrigerators as grow chambers. The compressor need not work—we're just using them as insulated boxes to lock in humidity. Plus they usually have shelves that you can arrange to suit your needs. 
They're kept indoors, so there isn't much fluctuation in temperature one way or the other. Comfortable temps for humans are comfortable temps for mushrooms, and if the cooler is kept indoors the temperature inside of it will eventually equalize with the temperature of its surroundings. Then all you'll need to do is get the humidity up in the cooler to between 80% and 85% and it'll be ideal for your favorite fruiting fungus. Fortunately, we have a fairly simple prototype for generating humidity and piping it into whatever space you might need to.
The build is super simple and the materials are pretty inexpensive. There's a link below to purchase the mist-maker, and all of the other materials can be picked up at any home improvement store. 

Materials

31- Quart Plastic Container
50-CFM Bathroom Exhaust Fan
Extension Cord
2" x 3" PVC reducer fitting and two  2" PVC extender fittings

How to make it!

The only tricky part of the entire build is getting those PVC fittings inserted in the top of the plastic container. Other than that it's pretty much all plug-and-play. You'll want to size the holes correctly so that the PVC fits snugly into them. That way you can seal it up and not lose any of the mist to the ambient environment. To size the opening most accurately, we recommend using a drill and hole saw set up:
You can pick up an inexpensive set of hole saws from Harbor Freight for about $15 if you don't want to spring for the fancy Milwaukee set which is quite a bit more expensive.

Use the hole saw to bore two holes in the top of the plastic container that the 2" PVC fittings tightly slide into.
Next you'll want to surround the fitting with some caulking to prevent the humidified air from escaping through the small gap between the fitting and the lid. Then drill another small hole (1/2") in the very center of the lid. This is where the power supply for the Mist Maker passes through. 
Insert the 3" x 2" PVC reducer coupling into one of the 2" extender fitting. This will help to better distribute the mist when it blows out of the chamber. Next, disconnect the union on the Mist Maker power supply, pass it though the hole in the center of the lid and reconnect it. The AC plug should be on the outside of the container and the Mist Maker head should be beneath the underside of the lid. Place the head in the plastic container and put the lid on. 
Next you'll want to connect the duct hose to the vent fan and to the 2" extender fitting. You can just slip it over the outside of both, or for added support affix the hose with a worm drive fastener (below left photo).
That's about the extent of the build/assemble! Now you'll just fill the container about two-thirds of the way full with water, plug in the Mist Maker and the vent fan (you'll use the extension cord for this—the plug on the vent fan only extends about one-half inch from its housing), and start humidifying!
With some extra duct tubing, you can pipe the humidified air into any chamber you want. Just attach the proper length of hose to the outlet on the left of the container in the picture above and run it to your grow chamber. Below is how we do it here at the AZMGA:
The vent fan blows air into the container which then pushes the air humidified by the Mist Maker out of the container, through the second length of duct hose, and into the grow chamber. To keep the air flowing, a hole sized to fit another 2" PVC extender fitting was bored on the side of the grow chamber opposite the humidification chamber. Another option, seen above right, is to wire in a humidistat to the power supply of the Mist Maker. Set it to turn on at 80% relative humidity and off at 85% and you'll have happily fruiting fungus!