I have never built this device but the plans were sent to me long ago by Ed Mohr . I thought some of you might find it to be of interest.

Build your own LED Flasher

This came out of a Radio Shack book. It is big that way you should be able to print it out and one is a pic of the one I built.
I also bought a socket for the 555 timer it had longer legs to solder to.

I also bought a small plastic box to put it in. (When Finished which I didn't yet) it takes time soldering this together.. it is polarity sensitive + or - if you hook the pos to the neg and the neg to the pos input you will burn some thing out.. (been there done that got the tee shirt) the only thing I was going to do was add a relay where the light goes that way I knew that the light was getting a full 12 volts + what do you think??
If you have any questions or suggestions sent them my way..hope this helps.

PS: hope you understand electronics I didn't and had to ask some questions so it you need some help JUST ASK and I will try to help I made mine to the print and didn't change the sizes of any resisters or capacitors.

(Click image to enlarge)