You have three options:

1. If you don't want to spend too much money, try your local thrift store first. I bought some maternity clothes there, much much cheaper but they are used.

2. If you don't mind spending money and want to feel the clothes before you buy them, you should go to local shopping mall.

3. Another place that's between choice 1 and 2 is Ebay. There are both used ones and new ones there for sale, and the price is cheaper than what you can buy from mall. The problem is you can't touch them until you actually bought them.