Your LHS is still the best place. Even if on-line stores offer a 30 or 40 cent per bottle savings over the shop in your area, the shipping & handling charges will negate any perceived savings. Unless you plan on ordering 20 or 30 bottles in a crack, go uptown..
Also, don't get too wrapped up in the small bottles and cans of a particular color. Many on-line and local camping & outdoor suppliers sell camo paints in large cans for hunters and their ilk... If building US Aircraft & armor are your main focus, for instance, getting the large spray cans of OD, flat black, brown, forrest green, and sand are worth it. Most of the OD and Tans are very, very close to FS shades, and will go a lot farther than hobby paints. Another thing is, if you have a buddy in the National Guard, have him pick you up some spray paint from his local armory. Those cans ARE actual FS shades of paint colors, and will only cost you a donation to the unit morale fund or family support group.
If it's a hard-to-find color, you may have to go on-line, but that isn't usually an issue with the brands you wasnt. Any of the E-stores advertised here and in FSM are pretty much all the same, as far as I know...