I am searching for this high and low. I have an iMac G4 800 15" lcd screen with Superdrive and an original Airport card in the slot within the base. I am using 10.2.8 with 512mb RAM.
I would like to upgrade to 802.11g. Airport extremebeing out I wondered whether a third party PC card (802.11g) might be found to do the trick. I know of an 802.11b Sony Vaio PC card (C150S) which works if one detaches the antenna (easy apparently) but have found no definitive proof (ie someone who has tried it) apart from being told a Buffalo card would theoretically work.
The search continues. I know the answer is out there.. Hope someone here can help.