I think you would need to look on eba- An AP .09 - .15 carb has enough meat on to convert, but there is no airbleed. It is 9mm, or .354" dia. The Cox .09 is a 5/16" - 32 thread (.312") It would be somewhat hard to hold in a lathe to turn the dia/thread. You can get the motor from H King for about the same $ as just a carb may be, and it puts out about the same power and comes with a muffler of sorts.
http://hobbyking.com/hobbyking/store...ow_Engine.html