Rocket engine

I want to have a little projekt. I'm intrested in technics and stuff, so I had an idea of building a rocket. I relized that that whould take pretty long time, so i thought, why don't build a rocket powered car?

The car whould be like 40 cm long and have 4 inlines (or something) wheels.
My question to you is, where can I find small rocket engine? I have seen some in catalouges but I whould like to see some other before I order.

Please don't tell me I'm crazy, I know this is a good idea, and I will show you some pictures when I (hopefully) build it.