Wanted Chapman Security System Part

[CortneyJKB]

I am looking for a part for a Chapman Security System. At least I believe it is a Chapman - that is the name on the little key thingy (I'm such a girl) that I have to plug in so I can start my car.
I do not know much about this system except it is very old and it isn't an alarm. It is a security system that is after market. It has a little slot that you plug in a little key-type thing. It looks like a computer chip. It disengages the ignition system when it is removed.
I NEED ANOTHER ONE!!!
Help? Anyone?
I have posted a picture of it below. It is only about 2 inches long. The chip part of it is about an inch.
Thanks to all!