For my solder paste fridge, I used an Igloo Kool Mate 36, which is a thermoelectric travel cooler. It came with a TEC, fan, heatsinks, etc. - it was basically already a refrigerator and I just added a precise way to control the temperature.
About a year later, the cooler stopped working (I think the fan died and it got really warm, but I can't remember exactly). I replaced it with a real compressor-style mini-fridge, which works much better because it can handle a much larger temperature differential inside/outside.
I wish I still had the cooler here because I could tear it apart and measure the size of the TEC.
You can get a rough idea of the scale of things from this photo:http://www.flickr.com/photos/mightyohm/ ... 404403515/
The heatsink was about 4" across. I don't think the TEC covered the entire heatsink, so it's entirely possible that it used a 40x40mm size TEC.
TECs are all over eBay, but if you want to get one with heatsinks, etc. I would try to find a used thermoelectric cooler like the one I used and use it for parts.