Sports equipment stores can, or large supermarkets, Wal-Mart has them anyway. But I suggest you go to Taobao to buy it, which is much cheaper. Just find a reputable online shop.

The chest muscles you practice are dumbbell sit-ups, then dumbbell flying birds, plus push-ups. These three movements should be the most classic. There are detailed videos on the Internet. Pay attention to safety and be sure to do it step by step.