I concur with Dr. Graubard regarding the ease of making Peltier devices.
You really don't need to spend lots of money to control the temperature
of your chamber; you can even get excellent feedback with microminiature
thermopiles that are the size of a pencil dot, and if you are willing to
make even greater efforts, build feedback controlled amplifiers that will
control temperature to a fraciton of a degree (something I didn't do, but
wouldn't hesitate doing if I needed to).  You could look at Horowitz and
Hill's excellent electronics text to enable you to build the right amp if
you needed; it isn't too difficult.
 
Tony Moss
Auburn