Yeah, I couldn't find it. The guy made it out of black foam board, and basically made a box tube, with walls that alternated top, bottom, and covered 2/3 the open area. The way it was made with the spacers and everything was really ingenious, so I wish I could find it. 2 black plumbing pipe (ABS) elbows work also.
It takes me so long to post, I try and reply but everyone beats me to it. Like was said, though, this is only going to make your heat issues worse.