There are dozens of lights that will fit in there, I used a group of 4 or 5 high output LED lights in a housing which required 2 holes for mounting and one for the wires. Ran the wires inside up to a fused output from the fuse box that got power with the key switch and they became driving lights that were on with the ignition.
You can kind of see them in this picture, the first car on the right, Black with the trailer.
Lights came off Ebay and were listed for a Mercedes. I think they were around $25 or so. I got them because they were sealed and rated at 14 volts which makes them last longer.
You always ask questions about stuff I did a few years ago. Hard to remember yesterday let alone 4 years ago!!