Some of the NAPA stores carry Amsoil stuff depending on who runs them and whatever the franchise stuff works. I'm surprised you're having problems finding some though; I keep coming across people that want me to buy it, even my real estate agent a few years ago had mentioned that her husband or brother or something was a dealer.
Many of my past Amsoil dealings were of the "come down to the basement, it's all down there" type, which is always awesome when you're dealing with strangers of various levels of creepy appearance in a remote cul-de-sac in a rundown neighborhood or in very rural areas of town.
How about you keep your Amsoil products in the garage instead, and preferably not with a really large chest freezer nearby?
I haven't bought Amsoil in a few years because of things like that, but that was in Colorado.
I think Universal Automotive in Concord sells Amsoil...