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Redrock LiveLens, or MTF Services, both make adapters that allow electronic iris control of Canon lenses. Other companies that may someday release adapters include Birger, Metabones, and Kipon, but if you want one that's available now your choices are Redrock or MTF.
Of course, there's also the Kipon iris adapter... that's in your price range...
http://www.amazon.com/Kipon-EOS-m4-Adapter-Aperture-Control/dp/B004XGFIZY
But it's not an electronic adapter, it has its own physical iris, so I wouldn't expect that it would meet your initial requirement of having it "work perfect"...
No electronic adapter exists in that price range
Thanks for the link I might use it in the meantine, problem is it looks like it only goes to f/2.8