Alternating flashing lights?

I am trying to figure out how I can make an alternating flash relay, the type used for wig-wag headlights.  I know there is a bunch of companies that sell this type of relay!

1.  I am too cheep to buy one.

2. I would probably ruin it taking it apart to see what makes it work (I do that alot!)

I want to use it with yellow lights on the back of my plow truck, I almost got smoked a few times today backing out of driveways that people could not see my roof light.

Thanks!

I was thinking that there might be a way with a standard signal light flashers and standard relays. 

All there is local is auto parts stores and a Radio Shack that doesn't even carry resistors anymore!

That is a real good drawing, but I don't have an alarm trigger (this could be a toggle swithc though I think) and it looks like the lights would flash at the same time like hazard lights.

What I need is for them to flash at different times, back and forth?

Let me know if this sounds right?

Im not sure if this setup will work and please excuese the size and crudeness. All i simply did was setup the relay to pulse a positive signal. This pulse can be changed by the size of the of capacitor to ground off of the relay. The 1st bulb pulses on, then moves to next capacitor, then flashes 2nd light. Please lemme know if this setup seems working. If i had a few bulbs and relays layin around the house i could have wired it up and tried a few thing... but this is the best i can come up with in my mind.