You may have better luck asking for light difusers though, I asked for egg crate at two different Home Depots and got looked at like I had 8 heads. Said light difuser and the light bulbs went on in their heads. Also check in those stores by where they have the drop ceiling things.. sometimes it's located there.
home Depot Lighting Dept... they always have about 8 bucks..
comes in 2'x4' panels if not in lighting look wear they have 2'x4' (drop0
ceiling tiles,,,
Thanks for everyone's replies but I took Pinkheine and Catdiggy's advice and went to Home Depot. Got myself a 2' by 4' panel of it, I'm sure that's plenty. Took me a while to find it though, I asked for lighting diffuser and it didn't work. I looked all over the lighting section and nothing. And lastly I asked my dad where plastic panels were and what you know...in the deep dark corner of Home Depot I dinf the eggcrates lol. Thanks for all the advice guys!