This is an Idea that I have been sitting on for a while.
the parts are:
a 56 quart plastic storage tub = $5.99
a sheet of acrylic = $5 ( was marked $10, I got it 50% discount at the close out of a surplus store, a retail piece to fit might run a bit more )
diffusion material to go under the acrylic. I used some baker's paper which happened to be the width of the acrylic. ( note: scotch tape was used to attach the paper to the top, but the baking paper is not very "stickable"
some sort of light shield material( to line the sides of the tub )
again, what I used was from the same surplus store. black plastic shiny on one side flat on the other. what you might use should be a neutral color.
a Sunpak 383 flash with a Sto-Fen and Pocket Wizard trigger:
The tub
The tub has a "draft" of about an inch-and-a-half. That is; the bottom dimension is a 3 inches less than the top. so I cut the side shields as trapezoids. the ends I left the ends "square" because it made an even split on the third piece of shield
call me cheap, I am.
Nice DIY! You're keeping the surplus store in business 
