Any optical drive should phsically fit fine. If you use one from an actual clamshell ibook the bezel should fit too. However if you use a trird party drive you will need to custom fit the bezel. The graphic chipset in the original ibooks is not very robust and may not support DVD playback. So movies may be out. However Data DVDs should work fine.
PB G4 15" 1.2ghz - Pismo G3 400 mhz - iBook G3 500 "Jukebox"
"SawSmurf" G4 500 - Quicksilver G4 Dual 1ghz modding...