I use zainostore.com, autogeek.net, pakshak.com, autopia-carcare.com, and a few others that escape me at the moment. Southwest Autoparts in South St. Louis has some decent meguiars products. Also, username "littleredm" has a good, cheaper product that I was impressed with, but I cannot remember the name of it. He owns a local detailing shop, AG Detailing (
www.ag-mobiledetailing.com/) and has some great advice.
For the most part, I've found it hard to find good products locally, so I just do a couple of big orders and plan ahead.