no plates
If you bought the car from a dealer they should have given you a temporary tag. If you bought it from an individual go to the Department of Motor Vehicles and register the car. See http://www.dmv.org/mo-missouri/vehicle-registration.php
I don't think anything you put in the window is going to defer the police. Driving responsibly will do it!
A temporary registration sticker. get it at dmv
You have to put a Rocket Launcher to take down police cars. Spikes to take down motorcycles. A EMP Weapon to take down helicopters. That will be enough for local, if you cross the border, that's a whole different story! :DOh, if you were worried about being ticketed instead of stopped, you could use a temporary tag you can get from your dealer. But even a good arsenal can fail in the job of stopping the police. :P Happy Asking