Light Switcher

I have a set of LEDs on 2 sides of a vehicle and i was wondering if there was an easy device that made them flash as follows

R__L
X__-
-__X
X__-
-__X

i was thinking of a way to use the same mechanism a blinker uses but insted of on, nothing, on, nothing, i was hoping for a left, right type thing. is there a device that can do that?

A 555 timer would do the trick

Mishael, that's red LEDs on the left at the top of the car and blue LEDs on the right at the top of the car, correct? Do you think the local law enforcement agencies would have a problem with your lights? Or did I assume incorrectly here?