Forever 21 has both regular and plus sizes (and I'm betting the plus selection in the Manhattan store is bigger than other stores) but only certain stores have the plus line, so you might want to check that out. Depending on how your weight is distributed though you might fit into some of the regular stuff just fine

So you can try that on too. Their stuff is really cute!
There are some other stores I like to head out to, but they're on Long Island so I'm not sure if you want to venture out that way (I checked, but there aren't any locations in Manhattan/Brooklyn).