I dressed as Lara Croft for a fancy dress party last week. I used the pictures of Lara's "Angel of Darkness" costumes on the Planet Lara website as a guide:
http://www.planetlara.com/nextgen/outfits.asp
I also took some elements from the look of the first movie (top and boots).
http://www.adventurersplace.com/laragear/outfits.htm
Black top: New Look
Camouflage shorts (cut down from trousers): Army surplus store
Belt: Army surplus store
Holsters: Black Viper leg holsters from Army surplus store
Guns (green guns painted silver and black using paint pens from a car accessories shop): Woolworths
Gloves: Ebay (but available in Army surplus stores)
I had the bag and boots, plaited my brown hair, and got white leg warmers to make the socks effect at the top of my high boots (couldn't find decent socks long enough and the leg warmers were really cheap).
I found it near impossible to get red round sunglasses. I bought some on Ebay but they arrived after my party. I didn't really need them to make the costume work. Instead I wore coloured contact lenses which made my eyes brown.