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First of all lets make sure you have a good bag to carry around. Be sure to take a very large, very light weight bag to carry all your purchases in. Make sure the handles are long enough and wide enough to go over your shoulder. Alternatively, and even better for your back, get a backpack.
There is I believe a rule that there are to be NO strollers or luggage racks on the trade floor. So using a cart type shopper may not be possible. Why not phone the Convention organisers and ask? If you can't use one of these then be sure to use the check-in area, if the convention has one. It will save your back and shoulders and will see things are reasonably safe while you do more shopping!
You also need to keep your money handy and safe. Use a bum bag. This wraps around your waist and allow you enough room for cash, credit card and maybe some personal ID. Secure your handbag and the rest of your purse with your hotel. (Ask them about what they can offer you here. Don't just leave it in your room!) Just take the minimum!