Brothers you need LEDs. There are two sizes of LEDs. Choice is urz. After that you need to buy 10ohm resistors accordingly as 12 volts will be provided to it by the batteries. I used duct which is used for protecting electric cables to prevent water from entering the LED circuit. Then sealed both ends with thesilicon gum. Moreover, i used screw driver (Made it hot) for making holes for entering LEDs from duct.
Then i connected the duct with the grill from the inside with the help of double tape and elfee. Thats it. It costed me 200Rs in total.