I have a GG&G front sight which I got from GG&G, and sent them my upper to have it installed on. Of course, I also have the GG&G MADD rear. If I'm not mistaken BM used to sell the GG&G stuff and install it, but I am guessing that now that they have their own that's no longer the case.
I like my flip sights, and for the project I'm building, having the front sight in place just wasn't going to work. Of course, I never have completed the project, and I've been shooting with the flipup sights all this time. They never seemed to have failed me in the past.