Here's a clue. http://www.macnn.com/news/22191 notes the ubiquitious Pioneer DVD 106 drive. You should be able to pick up this for the 100 buck range and try it.
I wanted to see about upgrading an internal CD drive on two mac G3 and a G4 towers. I can imagine the number of internal drives i can use will be pretty minimal given the way the case is designed. Can anyone make a recommendation for a burner that I can put in both that will work correctly?