breath alcohol sensor

I'm not to sure what kind of accuracy you are looking for so if you are looking for a cheap one to get the job done I would recommend looking on eBay. I found quite a few using the search term "breath alcohol". If you are looking for a little more sophistication I would recommend www.intex.com.

* KEEP IN MIND WITH MORE ACCURACY COMES MORE DIGITS ON THE PRICE TAG!!!

Here, $6.90 USD https://www.futurlec.com/Sensors.shtml and they ship from Thailand, so should get to you quickly.
Best wishes,
Robert