The most film-accurate Hamm I could find is the official Disney Pixar Hamm Bank that comes in the white Pixar box. He is a Disney Store exclusive and can still be found in most Disney stores. He looks great, he is film-accurate, and he is exactly what he is supposed to be, a piggy bank. Since he is meant to store coins, he is made of resin and has a smooth matt finish.
Although it would have been nice to have a Toy Story Collection Hamm that talks and moves, I think for an authentic Toy Story Collection, it makes sense to keep Hamm as a genuine piggy bank because that is exactly what he was in the movie. Although the Hamm Bank may not be the best toy, particularly for young children, as he could break if he is dropped, he is definitely a must have for any Toy Story fan and comes at a reasonable price.