I finally got around to building my temperature controller.
I used an electrical box from Home Depot (around 6x6x6"), a regular two-way switch (I want to be able to shut it all off completely, but it's not necessary), and a normal 3 prong outlet.
I used a drill bit to make holes in the corners on my template to make room for the controller, the switch, and the outlet, which I then connected with a jig saw, and finally finished the holes using a dremel with a mini drum sander. It would be easier/quicker to use the cutting tool for the dremel, but I didn't have one so I used what was available.
Here's what it ended up looking like:
I ended up mounting the outlet on the back on the thing, it could just as easily be mounted on the sides or under.