While its a good idea to contact each school individually, the purpose of getting non-science letters is to see that you are a well rounded, educated individual with more than just the ability to engineer (otherwise you should go to grad school and build bridges, quite literally).
There has to be someone, somewhere, some person that isn't involved in science. There has got to be some mentor, some dean, some counselor, something you've done whether it was theater lighting, painting, IM football, Call of Duty WarGamers Club, SOMETHING other than engineering. The power of the person writing the letter is not always as important as what is said.
Good luck, but be cautious about ignoring rules. Getting into medical school is 20% trying out the school and 80% selling yourself. Why take you when they could easily take you who did something else and could get the letter?