Here is an update for anyone interested. Attitude emailed me back stating that they do accept regular U.S. Postal Money Orders.
So the one i bought is good to go and on its way!
Sorry to revive an old thread but I am in a similar situation.
My post office says they cant make an international money order to the U.K. They said that they thought a normal Postal Money Order would do (although they seemed quite clueless).
So anyways, i bought one and it states on it...