After a bit more research, I found some other manufacturers of small DC compressors. Some of these are really small, and probably not suitable for a heating application, but look like fun nonetheless!
Aspen Systems Inc. – Mini Cooling Solutions » Our Technology These are made in the USA, and documentation is readily available on their website. Here's a blog entry showing one cut apart:
Mytek Controls: Aspen 1.9cc Compressor Dissected
And here are a few more DC compressors from the same company that makes the coke can compressors:
DC Compressor -
Enjoy!