Either BAM, as V suggests, or Artizan, or Black Tree. They all do squad packs, and I can speak from experience that the Black Tree Americans are really nice. The pics on the site don't do them justice.
Plus, they always seem to have a sale on. Just don't expect them to get to you quickly.
I also have a German squad from Westwind, with the seperate heads, which is quite nice, although they do sometimes have casting issues with their stuff.