Ahhh....then you're going to need full sheets and they have to be purchased locally. There are some great places to order online but for shipping purposes the full sheets will be cut to a size of 16X24. Being you need such a large sheet, I'd look in the yellow pages of my phone book and see if there's a glass shop close by. You may have to drive some distance to find a shop but a local glasser can cut the glass to *your exact measurments*.
Tell me this, are you intending to put a solid sheet of colored glass to cover existing glass, or is there a pattern you intend to do? I'm just a bit confused as to what you're doing.