Low budget zombie movies are another option. Say you have an idea for a zombie flick - go ahead and bring out the movie director in you. You don't need a lot of money to make a fun zombie movie for YouTube. You can get a camera for chump change these days, and you can get a plus size zombie costumes for even less. Just find one that suits your character and we'll have your size.
The cool thing about zombies on Halloween is that you can never have too many of them. You don't want to be the fifth Batman at the party, but there's nothing wrong with two, three, five or a dozen zombies. In fact, the more zombies you have, the better the costume works. There may be some competition for who has a better zombie costume, but that's part of the fun of Halloween. Be a member of the walking dead for Halloween in a plus size zombie costume that looks and fits like it should.