Some other information:
"The Effect of Pulse Width Modulation (PWM) Frequency on the Reliability of Thermoelectric Modules"
http://www.tetech.com/publications/pubs/ICT99MJN.pdf
Here's a commercial/industrial product:
http://www.zionscientific.com/series850.html
Got it! :
http://www.techcool.com/vpc/photo.htm