I would be weary to use these. In any lens the location of the diaphragm is critical, an add-on diaphragm is certainly not located optimally for any complex lens you might be using.
Yea maybe he is right, your much better off getting a regular adapter without an iris and trying to always at wide open without any semblance of control. I mean it is true that you can use this type of adapter with the iris set to wide open, and have it act like a regular adapter if you don't like the quality of the photos taken with its control, but why take the chance on finding that out? I mean you will probably waste many megabytes of digital photos and lots of minutes, maybe even up to or past an hour; I mean no way can that be worth it .. Your better off playing it safe and saving the extra eighty or so, dollars, or better yet just spend what ever you need to and buy the micro four third mount lenses that would be comparable to the EOS ones you have, or even just a couple hundred in manual lenses that have aperture control and the appropriate micro four third adapter.
And Gay, as for brand, I believe there's only one company that I know of who makes them. Also they do tell you that because it is not the best position for the iris of a lens that users found that you might not want to close it down too much because it wont get the best results, and best results for setting iris opening will vary depending on the lens.
Just look up the adapter on the auction sites and write the maker, or seller. I never found anyone that uses it written up online anyplace but its also has not been available for very long from my understanding. It also costs about one hundred and twenty dollars US; but i feel that if you have more than a few EF mount lenses you wish to use and at least one is of very good quality, it's worth trying out.