I believe
http://www.co2laser.com sells (or used to sell) a sealed CO2 laser and components to integrate it into your existing CNC gantry mill. It has been a while, but my recollection is that the 35 watt version was only around $3,000.
They currently (on the web site) sell a 25 watt laser "printer" which is a desktop box that will do 12" x 16" cutting or etching, around $10,000.