I purchased ours at Babies R US. They ship for free and you can usually find a coupon. Our mattress was 199.99 regular price but we got it for 160 plus tax. Here is the direct link http://www.toysrus.com/product/index.jsp?productId=2863621.
I found a site with some of the best crib mattresses, including some very good organic crib mattresses too. So nice not worrying about chemicals in my baby's bed.
We went to Healthychild.com to buy our organic crib mattress.
We bought one made from cotton and wool, and we really love it.
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