Opal glass would provide excellent diffusion (producing a Lambertian distribution of the light source), but might be difficult to work with in your lamps. You might try a fabric shop for translucent synthetic fabrics, a photo shop for diffusion film, or Amazon (see http://www.amazon.com/Rosco-Roscolux-Diffusion-Diffusing-Material/dp/B000B73OQY) for some material used in theater lighting.
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used on the Mars on EE Times Radio. Live radio show and live chat. Get your questions ready.