Take a look at this! 2 parabolic troughs combined to make a point focus! Answered
http://www.youtube.com/watch?v=FYzgYI9_h6s is from a Swedish mathematician.
He bounces light from one trough to the other to produce the point of light.
Even if it is not as efficient as a parabolic dish (2 reflections instead of 1) it must be easier!
He is just curving sheet material.
I have made parabolic dishes and it is really hard to be exact enough and it is really hard to get the reflective material to go onto the dish without crinkling. So under "real life" amateur conditions, his apparatus is likely to be as efficient as a home made parabolic dish!
He has more info http://www.youtube.com/user/MathRehab and he has pdf files to download too.
Great Idea. Hope someone makes an instructable.