In a pinch, you can buy them at the hotel. I get a pack on clearance at the end of the summer to bring with us. Well. of course the first time I forgot to pack them. It was February and we hit a cold patch so we only swam once. They daipers were at the hotel gift shop where they have the baby food and other baby items. They are the Huggies kind, but they are in a little plastic bag that says swim daiper - not Little Swimmers. They only thing is that they are $1, so iy you swim a lot or need to change a few times a day, all of a sudden it's costing more than the full pack.
I would try the local grocery stores and/or the Wall Mart and Target.