You could use a 556 timer, with half of it (one 555) in monostable mode with an inverter (can be made out of transistors). When a 555 is wired as a monostable timer, it switches the output on for a certain amount of time (triggered by a momentary push-button), and then shuts it off. The inverter would switch this around (off for a certain amount of time, i.e. 5-7 seconds, and then on). The second half of the 556 can be connected so that it is triggered by the first half, and times the output (connected to the light) so that it shuts it off after the desired time (30 seconds?). I'll see if I can work out a schematic for you, if you need it.
Do you have any soldering experience and equipment?
Overall, this sounds like a fun project. Good luck!
Der Strom
note: If you can't get a 556, you can simply use two 555s instead.