It's super cheating and probably takes a little practice, but if you're having an in-person conversation and your audience is looking at you, you can try to just mouth the M sound (essentially just open your mouth and continue the word without pushing air out during the beginning M). For example, "Margarita" would become "Argarita", but as long as you begin the word with your mouth closed to anybody listening it will still register as "Margarita." The mental gymnastics doing this might eventually rewire your brain/mouth to be able to push the whole word out at the same time. Not a speech pathologist, but spent my entire childhood with a vicious stutter which I eventually overcame in adulthood (98%).