Where can I rent outdoor lighting for a photo shoot?

My prom is on April 21st, and I was going to do an outdoor photoshoot, either in a shaded area or in the sun, depending on the weather. I live within 30 miles of New York City. I have a Nikon D5100, tripod, Neewer digital slave flash (http://www.amazon.com/NEEWER%C2%AE-Digital-Bracket-Cameras-Without/dp/B002X3VBFK/ and 6x8" flash diffuser, but I'm not sure what other equipment I'd need and how much it would cost.

You don't need a flash and flash diffuser and you don't need a tripod for outdoor, just a canmera will do, and a lens, maybe?

Outdoor lighting usually consists of a reflector and maybe a fill flash. You may need neither. A prom shoot is going to be all about the prom goers, so it is essentially portrait photography. Here are some tutorials on portrait photography.
http://www.digital-photography-school.com/how-to-take-portraits-19-portrait-photography-tutorials