Where to source the wireless interface boards for a G4 Mini?

I have a Mac Mini G4 that I bought from eBay for cheap, which is running the MorphOS operating system (the main reason why I got it). Unfortunately, it's a model without a wireless interface card included, so I have no wifi capability on it. I've tried searching eBay for the right part, but all results keep coming back with the AirPort Extreme card itself, which isn't what I need, or results for later Intel Mac Minis.

Does anyone know where I can get the right wireless interface board for the G4 Mini models? I'd like to be able to have some kind of connectivity for my Mac Mini; it's in a room away from my router and I can't be running cables too much at all.