You could try a major department store, like Bed Bath & Beyond, Home Outfitters, or Walmart. Smaller boutique stores that specialize in bath products, like Crabtree & Evelyn or the Body Shop, might have them as well.
I would try your local hardware stores, home depot, lowes. Also K-mart, Wal-mart, Target all carry bathroom accessories such as shower curtains. Another option to search online for local stores and then purchase at the store.