I use something called Metamorfix, but I think it might just be in Canada. I'm sure it's a water based MM, like you were talking about.
Anyway: I scrape some eyeshadow into a little Japanese sauce dish, and add a tiny drop of Metamorfix, stir it with my liner brush, and it lasts all day. I often use eyeshadow as eyeliner in this way, and the way I mix it keeps my shadows from getting weird hard spots on them from introducing moisture to the pan.
Oh, it makes the shadow more vibrant.