I searched the same thing out of curiosity a few months ago, and to my knowledge, none exist.
Personally, I think micro-switches would be very interesting, and I would at least want to try a keyboard made with them at least once! It looks like the only way you could get one is to either build one yourself, or have someone do it for you. I had the idea to build one using micro-switches, due to the reduced cost compared to mx switches, but I realized that you would also have to produce some custom key-caps. I do have access to a 3D printer, but even then, the time spent designing the keys would be immense!