Where can I find BPA-free baby bottle nipples online?

I have been searching for BPA-free baby bottle nipples via online stores lately, and to be honest, I was quite surprised that there are so many alternatives. Originally I thought that I would only order additional ones of the same type we already have. Though, after reading reviews and comparing materials, I came to realize that shapes and flow levels of different bottle nipples may vary in their effectiveness, according to the baby. I spent the better part of several evenings at Amazon, Alibaba and a couple of local baby stores online just to look at prices, packaging and read reviews from other parents. Some product pages highlighted softer silicone, while others were talking about anti-colic features or slower flow designed for younger babies. Fellow parents, what is your go-to place for buying baby bottle nipples online, and do you recall if there were some particular brands or types of materials that your baby found more comfortable?