I recently bought some inexpensive LEDS and a strap switch from Model Train Software. I got their Fire set, 6 red LEDS and a battery connector/switch for like $20, including shipping.
http://www.modeltrainsoftware.com/
For the Viper, you could just get 3 LEDs for the engines, and one for the cockpit display (which is clear, if I remember correctly), and the battery /switch for about $15 total, shipping included.
The nice thing about these LEDs is that the resistor is already attached to them - no need for soldering. They're bright, come in several colors, and are super easy to use. I've actually considered getting another Viper kit just to wire it up w/ these.