Has it been documented anywhere whether Apple was using the same displays in these iMacs as in their 15" and 17" laptops at the time? That would make it simpler to try to find replacements without first disassembling the display (mine has a minor defect that I'd like to resolve with replacement, but doesn't make the iMac unusable as-is)
Being that there were three/four different variants of the G4 15", which do you have? They may have different panels internal, depending on model. Once you know which one you have, finding a similar panel equivalent on Panelook.com might help in your search. I am going to assume it is some LG/Philips panel.