Interior light delay modification

Hi,

I plan to make a modification to my right interior-light. That's that one near the keyhole. I want this light to stay on for 30 more seconds than the rest of the interior light when you close the door. In that way I have time to find my keyhole in the dark.

I could build in extra LEDs to do the job just as Peter Wu did

, but I'd like to use the existing materials... Now, my knowledge of electronics is not large. That's why I need your help. Can I just connect a large capacitor and diode before the light or is more required?

Thanks!

Jeroen The Netherlands