Not sure what exactly you are looking for. A replacement dome light? If so, it might just be a burned out bulb. You can access it by removing the two 'fish eyes' (using your fingernail) and then the 2 torx screws (T30 IIRC) behind the eyes. This will drop the entire center latch mechanism and you'll plainly see the bulb holder in the middle. I think the replacment is 5W.
Now, if you are looking to add more lighting to the interior you can add footwell lights as I did:
Basically I bought 2 trunk lights (p/n 997.632.201.00 at $2.75 each w/ the bulb) and ran them off the dome light. I changed out their stock bulb (10W) to 5W ($5). Then I mounted one in the black foam liner in the passenger footwell and the other in a piece of plexiglass/lexan in the driver footwell (screwed into the HVAC duct as you can see above). They turn on with the dome light hen you: manually turn it on, unlock the car or open a door and dim/fade out as well.
Some people have added LEDs.
Hope this helps.