I don't think there's an electric air conditioner available for the Skymaster. Personally, even if there was, the Skymaster electrical system is kind of whimpy, and I wouldn't consider loading it up with such an add on.
That said, if you're open to a mechanically driven air conditioner, Riley has one that works very well. However, it does add a scoop to the belly which would interfere with a belly pod.
http://www.superskyrocket.com/pages/stckits.htm